Sample Paper – 2011
Class – XII
Subject –Physics
Class – XII
Subject –Physics
Time: 3 Hours Max. Marks: 70
General Instructions:
(i) All questions are compulsory.
(ii) Question numbers 1 to8 are very short answer type questions, carrying one mark each,
(iii) Question numbers 9-18 are short answer type question, carry two marks each.
(iv) Question numbers 19to27 are also short answer type question, carrying 3 mark each.
(v) Question number 28to30 are long answer type question carrying five marks each.
(vi) Use log tables for necessary calculations.
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1. Which are of the following will describe the smallest circle when projected with the same velocity v perpendicular to the magnetic field B (i) α particle and (ii) β particle?
2. In a series LCR circuit the voltage across inductor, a capacitor and a resistor are 30 V, 30 V and 60 V respectively. What is the phase difference between applied voltage and current in the circuit?
3. Write the truth table for the following combination of gates :
4. The charging current for a capacitor is 0.25 A, What is the displacement current across its plate?
5. What changes in the focal length of a (1) concave mirror and (ii) convex lens occur, when the incident violet light on them is replaced by red light
6. Compare the radii of two nuclei with mass number 1 and 27 respectively.
7. A lamp is connected in series with an inductor to a d.c. source. What will happen to its glow, when it is connected directly to the same source?
8. How does the energy gap in a semiconductor vary, when doped with a pentavalent impurity?
9. An electric dipole is held in a uniform electric field.
(i) Show that no force acts on its
(ii) Derive an expression for the torque acting on it.
10. 4 identical cells, each of emf 2 v are joined in parallel providing supply of current to external circuit consisting of two 15 W resistance joined in parallel. The terminal voltage of the cells, as read by an ideal voltmeter is 1.6 volt. Calculate the internal resistance of each cell.
11. For the same angle of incidence the angles of refraction in three media A , B , C are 150 , 250, and 350 respectively. In which medium the velocity light is minimum.
12. A compass needle, pivoted about the horizontal axis, and free to move in the magnetic meridian, is observed to point along the :
(i) vertical direction at place A
(ii) horizontal direction at a place B.
Give the value of the angle of dip at these two places
13. Identify the part of the electromagnetic spectrum to which is
(i)Suitable for radar system used in aircraft navigation.
(ii)Adjacent to low frequency end of the electromagnetic spectrum.
(iii) Produced in nuclear reactions.
14. A uniform wire of resistance 1W cm-1 is bent in the shape of letter A, the sides of letter are 30cm each and the cross piece in the middle is 15 cm long while the apex angle is 600. find the resistance of letter between the two ends of legs.
15. Draw a graph showing the variation of stopping potential with frequency of incident radiations in relation to photoelectric effect. Deduce an expression for the slope of this graph using Einstein’s photoelectric equation.
16. The following table gives the value of work function for a new photosensitive metal.
S.No | Metal | Work Function (eV) |
1 | Na | 1.92 |
2 | K | 2.15 |
3 | Mo | 4.17 |
In each of these metals is exposed to radiations of wavelength 300 nm which of them will not emit photoelectrons and why?
17. The ground state energy of hydrogen atom is -13.6 ev. What is the kinetic and potential energies of the electron in this state?
OR
A radioactive isotope has a half life of T years. How long will it take the activity to reduce (i) 3.125% (ii) 1% of its original value?.
18. Draw the block diagram of a communication system. what are analog and digital signals?
19. Two point charges A and B of value +5 x 10-9 C and +3 x 10-9C are kept 6cm apart in air. Calculate the work done, when charge B is moved by 1cm towards charge A.
20. In the following network of capacitors, find the equivalent capacitance and total charge and potential difference across each capacitor.
21. Using Kirchhoff’s laws, calculate the value of the electric currents, I1, I2 and I3 in the given electrical network.
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OR
AB is 1 meter long uniform wire of 10 ohm resistance. The other data are as shown in the circuit diagram given below :
Calculate (i) potential gradient along AB, and (ii) length AO of the wire, when the galvanometer shows no deflection.
22. Derive Snell’s law of refraction by drawing the refracted wave front corresponding to a plane wave front incident on the boundary separating a rarer medium from a denser medium.
23. Define resolving power of a compound microscope. How does the resolving power of a compound microscope change when
(i) refractive index of medium between the object and objective lens increases. (ii) wavelength of radiation is increased.
24. A sinusoidal voltage V=200sin 314t is applied to a resistor of 10 ohm resistance. Calculate
a. Rms value of voltage
b. Rms value of current
c. Power dissipated as heat in watt
25. Consider the situation shown in fig. The wires P1Q1 and P2Q2 are made to slide on the rails with the same speed 5 cm/ s. Find the electric current in the 19 ohm resistor if (a) both the wires move towards right and (b) if P1Q1 moves towards left but P2Q2 moves towards right.26. The energy levels of an atom of element are shown in the following diagram. Which one of the level transitions will result in the emission of photons of wavelength 620 nm ?
Support your answer with mathematical calculations.
27. Explain the need of modulation. Derive an expression for covering range of TV transmission towers.
28. Define the terms ‘potential barrier’ and ‘depletion region’ for a p – n junction. Explain, with the help of a circuit diagram, the use of a p – n diode as a full wave rectifier. Draw the input and output wave forms.
OR
Draw a labelled circuit diagram of a common emitter amplifier using a p-n-p transistor. Define the term voltage gain and write an expression for it. Explain how the input and output voltages are out of phase by 1800 for a common-emitter transistor amplifiers.
29. State and prove Amperes circuital law. Use Amperes circuital law. To obtain an expression for the magnetic field within a long solenoid
OR
State Biot savart law .use it to derive an expression for the magnetic field due to a current carrying circular loop of N turns and radius R, at a point distance x from its centre on the axis of the loop
30. Derive the expression for the fringe width in Young’s double slit interference experiment.
If one face of a prism of prism angle 30o and m = 
is silvered, the incident ray retraces its initial path. What is the angle of incidence ?
is silvered, the incident ray retraces its initial path. What is the angle of incidence ?OR
Derive an expression for the width of the central maxima for diffraction of light at a single slit. How does this width change with increase in width of the slit.
Two polaroids are placed 90o to each other and the transmitted intensity is zero. What happens to the intensity of transmitted light when one more Polaroid is placed between these two bisecting the angle between them ?
Paper Sumitted By:
Name : arun joshi
Email : arunjoshi_67568@rediffmail.com
Phone No. 09414827275Sample Paper – 2011
Class – XII
Subject -Physics
Class – XII
Subject -Physics
Time: 3 hours Max. Marks: 70
General Instructions:
1. All questions are compulsory.
2. Internal choices have been provided in some questions. You have to attempt only one of the choices in such questions.
3. Questions 1 to 8 are very short answer type question carrying 1 mark each.
4. Questions 9 to 18 are short answer type question carrying 2 marks each.
5. Questions 19 to 27 are also short answer type question carrying 3 marks each.
6. Questions 28 to 30 are very long answer type question carrying 5 marks each.
7. Use log tables, if necessary.
Q.1 Arrange the given electromagnetic radiation in descending order of their frequencies: Infrared Rays, UV rays and gamma rays.
Q.2 The graph shows the variation of voltage ‘V’ across the plates of two capacitors A and B versus charged on them. This of the capacitors has higher capacitance?
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Q.3 A charged particle moving with velocity ‘v’ as shown in figure experiences an upward force. What force. What is the charge sing on the particle?
F >
> S
>
V
Q.4 Light of wavelength 6000A0 in air enters a medium of µ=1.5. What will be its frequency in the medium ?
Q.5 Name the physical quantity whose S.I. unit is J/C.Is it scaler or a vector quantity?
Q.6 The ground state energy of H-atom is -13.6 ev.What are the kinetic and potential energies of electron in this state?
Q.7 Force is given by F=q*(V*B) of these name the pairs of vector which are always at right angles to each other.
Q.8 Two thin lenses of power +6D and -2D are in contact. What is the focal length of the combination?
Q.9 Obtain the binding energy of the nuclei 26Fe56 in units of eV from the following data:-mfe=55.934939u, mn=1.008665u and mp =1.007825u.
Q.10 Distinguish between point to point and broadcast communication mode. Give one example of each.
Q.11 If the current sensitivity of a moving coil – galvanometer is
increased by 20%, its resistance also increase by 1.5 times, How will the voltage sensitivity of the galvanometer
be affected ?
Q.12 The flux of the electrostatic field through the closed spherical surface‘s’ is found to be 4 times that through the closed spherical surface S. Find the magnitude of the charge Q. Given q1 = 1 uc, q2 = - uc, q3 = 9.854 uc.
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Q.13 What does the term LOS communication mean? Name the types of waves that are used for this communication. Which of the two height of transmitting anteena and height of receiving anteena can affect the range over which this mode of communication remains effective?
Q.14 State Joulis law of heating by electric current. Name the materials used for making
(i) Heater Element (ii) Standard resistors.
Q.15 In the following circuit a meter bridge is shown in its balanced state. The meter bridge wire has a resistance of 1Ω/cm.Calculate the value of unknown resistance ‘X’ and the current drawn from the battery of negligible internal resistance.
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Q.16 A right angled crown glass prism with critical angle 410 is placed between the object PQ in two positions as shown in the figures (i) and (ii). Trace the path of rays from ‘P’ and ‘Q’ passing through the prisms in the two cases.
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Q.17 Violet light is incident on a thin convex lens. If this light is replaced by red light, explain with reason, how the power of this lens would change?
Q.18(a) Draw a graph showing the variation of potential energy of a pair of nucleons as a function of their separation. Indicate the region in which nuclear force is
(i) Attractive and (ii) Repulsive
(b) Write two characteristic features of nuclear force which distinguish it from the Coulomb force.
Q.19 Distinguish between frequency modulation and amplitude modulation. Why is an FM signal less susceptible to noise than an AM signal?
Q.20 What is an intrinsic type of semiconductor? How can this
material be converted into (i) P – type (ii)N-type extrinsic
semi conductor. Explain with the help of energy band diagram.
Q.21 Define the term decay constant of a radio active nucleus. Two nuclei P, Q have equal no. of atoms at t = 0. Their half lives are 3 hours and 9 hours respectively. Compare their rates of disintegration, after 18 hours from the start.
Q.22 Deduce an expression for the self – inductance of a long solenoid of ‘N’ terms, having a core of relative permeability µr.
Q.23 A double convex lens of glass of refractive index 1.6 has its both surfaces of equal radii of curvature of 30 cm each. An object of height 5 cm is placed at a distance of 12.5 cm from the lens. Calculate the size of the image formed.
Q.24 Mention the significance of Davison – Germer experiment and ά – particle and a proton are accelerated from rest through the same p.d ‘V’. Find the ratio of de – broglie wave length associated with them.
Q.25 What is the effect on the interference frindges in a young’s double slit experiment due to each of the following operations:
a) The screen is moved away from the plane of the slits;
b) the (monochromatic) source is replaced by another (monochromatic) source of shorter wavelength;
c) The separation between the two slits is increased
Q.26 A resistance of R ohm draws current from a potentiometer. The potentiometer has a total resistance Ro ohm as shown in figure.
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A voltage ‘V’ is supplied to the potentiometer. Derive an expression for the voltage across ‘R’ when the sliding contact is in the middle of the potentiometer.
Q.27 Derive an expression for the energy stored in a parallel plate capacitor ‘C’ with air as the medium between its plates and having charges ’Q’. show that energy can be expressed in terms of the electric field as where ‘A’ is the area of the plate and ‘d’ is the separation between the plates.
‘OR’
Define the term dipole moment of an electric field indicating its direction. Write its S. I. unit. An electric dipole is placed in a uniform electric field , deduce an expression for the torque acting on it. In a particular situation, it has its dipole moment aligned with the electric field. Is the equilibrium stable or unstable?
Q.28 (a) Draw a ray diagram to show the refraction of light through a glass prism. Hence obtain the relation for the angle of deviation in terms of the angle of incidence, Angle of emergence and the angle of the prism.
(b) A right angled isosceles glass prism is made from glass of refractive index 1.5. Show that a ray of light incident normally on :
(i) One of the equal sides of this prism is deviated through 900.
(ii) The hypotenuse of this prism is deviated through 1800.
OR
Q.(a) With the help of a labeled ray diagram, show the image formation by a compound microscope. Derive an expression for its magnifying power.
(b) How does the resolving power of a compound microscope get reflected on:
(i) Decreasing the diameter of its objective?
(ii) Increasing the focal length of its objective.
Q.29 Define the term wavefront. Draw the wavefront and corresponding rays in the case of a
(i) Diverging spherical wave .
(ii) Plant wave.
Using huygen’s construction of a wavefront, explain the refraction of a plane wavefront at a plane surface and hence verify Snell’s law.
OR
Q. Derive the relation between the focal length of a convex lens in terms of the radii of curvature of the two surfaces and refractive index of its material. Write the sign conventions and two assumptions use in the derivation of this relation.
Q.30(a) Draw the circuit diagrams of a p-n junction diode in (i) forward bias (ii) reverse bias. How are these circuit used to study the V-I characteristics of a silicon diode? Draw the typical V-I characteristics.
(b) What is a light emitting diode(LED)? Mention Two important advantages of LEds over conventional lamps.
OR
Q.(a) Draw the circuit arrangement for studying the input and output characteristics of an n-p-n transistor in CE configuration. With the help of these characteristics define (i) Input resistance (ii) Current – amplification factor.
(b) Describe briefly with the helf of a circuit diagram how an n-p-n transistor is used to produce self – sustained oscillations.
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Paper Submitted by
Name : CHITRA SHARMA
Email : lovely17oct@gmail.com
Phone No. 9456075675
Sample Paper- 2011
Class- XII
Subject – Physics (ELECTROSTATICS)
Time Allowed: 3 hours Maximum Marks: 70
(a) All questions are compulsory
(b) Question numbers 1 to 8 are very short answer type questions, carrying one mark each.
(c) Question numbers 9 to 18 are short answer type questions, carrying two marks each.
(d) Question numbers 19 to 27 carry three marks each.
(e) Question numbers 28 to 30 are long answer type questions, carrying five marks each.
(f) Use of calculators is not permitted. However, you may use log tables, if necessary.
Q.1> How many protons will have the total charge of 1C
Q.2> What is the dielectric constant of Silver?
Q.3> Find the electric field b/w 2 metal plates 5mm apart, connected by a 12V battery.
Q.4> Write the value of Coulomb constant ( K ) and mention its units.
Q.5> Find the work done in placing a charge of 8nC on a condenser of capacity 100micro-farad.
Q.6> Define equipotential surface and draw EPS for a single point charge.
Q.7> What is the angle b/w electric dipole moment and the electric field on its equatorial point?
Q.8> Sketch electric field lines for a dipole.
Q.9> The electrostatic force on a small sphere of charge 4C due to another small sphere of charge 8C in air is F. What is the distance b/w the 2 spheres. What is the force on the –8C sphere due to the first sphere. What will the force be if the spheres are dipped in a liquid having dielectric constant K
Q.10> An electron is placed inside a capacitor ( 5μf ). It is found to be stationary i.e. its weight is balanced by the electrostatic force. Find the potential difference across the plates of the capacitor if the plate area is A.
Q.11> Equal charges each of 1C are placed at x = 0, 2, 4, 8, 16 cm. Find force experienced by the charge at x=2 cm.
Q.12> What is the work done in moving a charge 100nC from point A to point B 5cms apart, where both points A and B lie on the same equipotential surface? Explain your answer.
Q.13> Define electric flux. Is it a vector quantity? Give its units. If the flux entering and leaving a closed surface is Φ1 and Φ2 find the charge inside that surface.
Q.14> Define electric potential. Write the expression for potential due to a point charge.
Q.15> Can a positively charged object attract a neutral object? Explain briefly
Q.16> Write 2 differences b/w charge and mass.
Q.17> A uniform electric field E exists b/w the 2 charged plates as shown in the
figure. What would be the work done in moving a charge q along the A B
ABCDA. Hence define conservative fields and give 2
properties of electrostatic forces.
D C
Q.18> Calculate the potential at the center of a square of side √2 m, which
carries at its 4 corner charges of 2nC , 1nC , -2nC , -3nC respectively.
Q.19> Two point charges 4q and q are fixed a distance 2m apart. Find the point on the line joining them at which the net electric field intensity in zero. What is the potential at this point.
Q.20> Charges of 4μC each are placed at the four corners of a
square of side 1m. Find the electric field and potential at the center.
What would these quantities be if one of the given charges were negative?
Q.21> State Coulomb’s law in vector form
Q.22> When 2 capacitors C1 and C2 are connected in series the net is 1.2 farad, when connected in parallel the net capacitance is 5 farad. Find C1 and C2.
Q.23> Find the equivalent capacitance b/w points A and B.
Each capacitor is of 1μfarad B
A
Q.24> State Gauss’s theorem. Give its mathematical expression. Derive an expression for the electric field intensity due to a hollow spherical shell of radius R and charge of density σ C/m2
Q.25> Two point electric charges A and B of unknown magnitude and sign are placed d distance apart. The electric field is zero at a point, not b/w the charges but on the line joining them and closer to A. Write 2 essential conditions for this to happen
Q.26> Explain dielectric polarization. A certain region of space is to be protected from external electric field. Suggest a suitable method.
Q.27> What are electric field lines? Give 4 properties and define neutral point.
Q.28> Define capacitance and give its units. Explain the principle of
a parallel plate capacitor and the use of earthing. Derive the formula
for capacitance of a parallel plate capacitor with a slab.
Q.29> Describe the construction and working of the VanDe Graff generator.
Q.30> Use Gauss’s law to obtain the electric field due to an infinitely long straight uniformly charged wire.
(b) Electric field in the given figure is directed along + X direction and given by Ex = 5Ax + 2B, where E is in NC-1 and A = 10 and B = 5 in SI units. x is in meter. Calculate the electric flux through the cube and net charge enclosed within the cube. The side of the cube is 10cm/
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If you have any doubts, please write to
Abhishek Gupta
Dept of Physics
I.I.T.-Delhi
Email: physics_css@yahoo.com
Sample Paper – 2011
Class – XII
Subject – Physics
Class – XII
Subject – Physics
Sample paper 1
Question 1. What is the work done in moving a charge of 10 nC between two points on an equipotent surface? (1 mark)
Question 2. Name the device used for measuring the internal resistance of a secondary cell? (1 mark)
Question 3. What is the nature of magnetic field in a moving coil galvanometer? (1 mark) a
Question 4. If a rate of change of current of 2 A/s induces an e.m.f.of 10mV in a solenoid, what is the self -inductance of the solenoid? (1 mark)
Question 5. What type of magnetic material is used in making permanent magnets? (1 mark)
Question 6. Two metals A, B have work-functions 2eV, 4eV respectively. Which metal has lower threshold wavelength for photoelectric effect? (1 mark)
Question 7. Which part of the electromagnetic spectrum is used in operating RADAR? (1 mark)
Question 8. Which type of biasing gives a semiconductor diode very high resistance? (1 mark)
Question 9. An electric dipole, when held at 300 with respect to a uniform electric field of 104N/C, experiences a torque of 9 x 10-26Nm. Calculate the dipole moment of the dipole. (2 marks)
Question 10. A set of n identical resistors, each of resistance R ohm, when connected in series have an effective resistance X ohm and when the resistors are connected in parallel, their effective resistance is Y ohm. Find the relation between R, X and Y. (2 marks)
Question 11. State Kirchhoff's rules for electrical networks. (2 marks)
Question 12. Show that Lenz's law is in accordance with the law of conservation of energy. (2 marks)
Question 13. Draw a labeled diagram of Hertz's experiment for producing electromagnetic waves. (2 marks)
Question 14. Give two differences between fringes formed in single slit diffraction and Young's double slit experiment. (2 marks)
Question 15. Light of wavelength 600nm is incident on an aperture of size 2mm. Calculate the distance up to which the ray of light can travel such that its spread is less than the size of the aperture. (2 marks)
Question 16. Explain the principle used in Bunsen's grease photometer to compare the illuminating powers of two light sources. (2 marks)
Question 17. A ray of light while traveling from a denser to a rarer medium undergoes total internal reflection. Derive the expression for the critical angle in terms of the speed of light in the respective media. (2 marks)
Question 18. Draw a graph showing the variation of binding energy per nucleon with mass number of different nuclei. Mark the region where the nuclei are most stable. (2 marks)
Question 19. Name the logic gate shown in the diagram and give its truth table. (2 marks)
Question 20. State and explain Seebeck effect. (2 marks)
Question 21. Explain with the help of a circuit diagram how the value of an unknown resistance can be determined using a Wheatstone bridge. Give the formula used. (3 marks)
Question 22. Earth receives an amount of heat radiation 1.4 x 103 W/m2 from the sun. Assume that earth re-emits all the radiation received from the sun. Calculate the surface temperature of the earth. (3 marks)
Question 23. A straight wire carries a current of 3A.Calulate the magnitude of the magnetic field at a point 10cm away from the wire. Draw diagram to show the direction of the magnetic field. (3 marks)
Question 24. Explain how a vibration magnetometer can be used to determine the magnetic moment of a bar magnet. (3 marks)
Question 25. Deduce lens maker's formula for a thin biconvex lens. (3 marks)
Question 26. Explain the origin of spectral lines of hydrogen using Bohr's theory. (3 marks)
Question 27. A beam of electrons passes unelected through mutually perpendicular electric and magnetic fields E and B respectively. If the electric field is cut-off ,the electron beam moves in a circular path of radius 'r'.Derive the expression for e/m of electrons in terms of r,E and B. (3 marks)
Question 28. Draw a labeled diagram of Van de Graff generator. Give its principle and explain its working. (5 marks)
Question 29. Prove that the power dissipated in an ideal resistor connected to an a.c. source is V2eff/R.Acapacitor,a resistor and a 40 mH inductor are connected in series to an a.c. source of frequency 60 Hz. Calculate the capacitance of the capacitor, if the current is in phase with the voltage. (2+3 marks)
Question 30. Explain with the help of a circuit diagram the working principle of a transistor as an amplifier in the common emitter configuration .Derive the expression for the voltage gain of the amplifier.(5 marks)
Sample paper no 2
Question 1. Horizontal component of Earth's magnetic field at a place is 3 times the vertical component. What is the value of angle of dip at this place? (1 mark)
Question 2. Force between two point electric charges kept at a distance d apart in air is F. If these charges are kept at the same distance in water, how does the force between them change? (1 mark)
Question 3. Give any two factors on which thermo-electric emf produced in a thermo-couple depends. (1 mark)
Question 4. The electric current in a wire in the direction from B to A is decreasing. What is the direction of induced current in the metallic loop kept above the wire as shown in the figure? (1 mark)
Question 5. Name the electromagnetic radiations used for viewing objects through haze and fog. (1 mark)
Question 6. Give the ratio of the number of holes and the number of conduction electrons in an intrinsic semiconductor. (1 mark)
Question 7. In the given diagram, is the diode D forward or reversed biased? (1 mark)
Question 8. Name the planet which has maximum value of albedo. (1 mark)
Question 9. Two point electric charges of unknown magnitude and sign are placed a distance’d’ apart. The electric field intensity is zero at a point, not between the charges but on the line joining them. Write two essential conditions for this to happen. (2 marks)
Question 10. The variation of potential difference V with length l in case of two potentiometers X and Y is as shown in the given diagram. Which one of these two will you prefer for comparing emf's to two cells and why? (2 marks)
Question 11. Name any one material having a small value of temperature coefficient of resistance. Write one use of this material. (2 marks)
Question 12. Write two advantages and two disadvantages of a secondary cell over a primary cell. (2 marks)
Question 13. In the figure, the straight wire AB is fixed while the loop is free to move under the influence of the electric currents flowing in them. In which direction does the loop begin to move? Give reason for your answer. (2 marks)
Question 14. A radio frequency choke is air-cored coil whereas in audio frequency choke is iron-cored. Give reasons for this difference. (2 marks)
Question 15. An astronomical telescope consists of two thin lenses set 36 cm apart and has a magnifying power 8. Calculate the focal lengths of the lenses. (2 marks)
Question 16. Use the mirror formula to show that for an object lying between the pole and focus of a concave mirror, the image formed is always virtual in nature. (2 marks)
Question 17. An £-particle and a proton are accelerated through the same potential difference. Calculate the ratio of velocities acquired by the two particles. (2 marks)
Question 18. Describe the method used for determination of distance of a planet by parallax method. (2 marks)
Question 19. Explain the principle of a tangent galvanometer. How does the reduction factor of the galvanometer change, when (i) number of turns of the coil is increased and (ii) radius of the coil is decreased? Give reason for your answer in each case. (3 marks)
Question 20. A wire of uniform cross-section and length l has a resistance of 16 ohm. It is cut into four equal parts. Each part is stretched uniformly to length l and all the four stretched parts are connected in parallel. Calculate the total resistance of the combination so formed. Assume that stretching of wire does not cause any change in the density of its material. (3 marks)
Question 21. An electric heater and an electric bulb are rated 500 W, 220 V and 100 W, 220 V respectively. Both are connected in series to a 220 V a.c. mains. Calculate the power consumed by (i) the heater and (ii) electric bulb. (3 marks)
Question 22. Why is diffraction of sound waves easier to observe than diffraction of light waves? What two main changes in diffraction pattern of a single slit will you observe when the monochromatic source of light is replaced by a source of white light? (3 marks)
Question 23. Explain surface wave and sky wave propagations of radio waves. Why is short wave communication over long distances not possible by surface wave propagation? (3 marks)
Question 24. Give reasons for following observations on the surface of moon: (3 marks)
(i) Sun-rise and sun-set are abrupt
(ii) Sky appears dark
(iii) A rainbow is never observed.
Question 25. The energy levels of an atom of element are shown in the following diagram. Which one of the level transitions will result in the emission of photons of wavelength 620 nm? Support your answer with mathematical calculations. (3 marks)
Question 26. Give the logic symbol and truth table for AND gate. Explain, with the help of a circuit diagram, how this gate is realized in practices. (3 marks)
Question 27. Drawing a labeled circuit diagram, explain how a NPN transistor can be used as an amplifier in common base configuration. (3 marks)
Question 28. Explain the effect of introducing a dielectric slab between the plates of a parallel plate capacitor on its capacitance. Derive an expression for its capacitance with dielectric as the medium between the plates.
Or
Give the principle and explain the working of a Van de Graaff generator with the help of a labeled diagram (Marks 5)
Question 29. Explain the process of release of energy in a nuclear reactor. Draw a labeled diagram of a nuclear reactor and write the function of each part. (5 marks)
Question 30. Draw a labeled diagram of Thomson's experimental set-up to determine e/m of electrons. Explain by deriving the necessary mathematical expression how of electron can be determined by this method. (5 marks)
Sample paper 3
Physics Class XII
Question 1. Draw an equipotent surface in a uniform electric field. (1 mark)
Question 2. If a wire is stretched to double its original length without less of mass, how will the resistivity of the wire be influenced? (1 mark)
Question 3. Why do magnetic lines of force prefer to pass through iron than through air? (1 mark)
Question 4. What is the power factor of an LCR series circuit at resonance? (1 mark)
Question 5. Why is the transmission of signals using ground waves restricted to frequencies upto 1500 kHz? (1 mark)
Question 6. The polarizing angle of a medium is 60o. What is the refractive index of the medium? (1 mark)
Question 7. How does the collector current change in a junction transistor, if the base region has larger width? (1 mark)
Question 8.Two stars A and B have magnitudes -2 and +4 respectively. Which star appears brighter? (1 mark)
Question 9. An electric flux of -6 x 103 Nm2/C passes normally through a spherical Gaussian surface of radius 10 cm, due to a point charge placed at the center.
(i) What is the charge enclosed by the Gaussian surface?
(ii) If the radius of the Gaussian surface is doubled, how much flux would pass through the surface? (2 marks)
Question 10. Three identical resistors, each of resistance R, when connected in series with a d.c. d.c.
Question 11. Define mutual inductance. State two factors on which the mutual inductance between a given pair of coils depends. (2 marks)
Question 12. Light from a galaxy, having wavelength of 6000 Ao, is found to be shifted towards red by 50 Ao. Calculate the velocity of recession of the galaxy. (2 marks)
Question 13. A converging lens has a focal length of 20 cm in air. It is made of a material of refractive index 1.6. If it is immersed in a liquid index 1.3, what will be its new focal length? (2 marks)
Question 14. Draw a labeled ray diagram to show the image formation in astronomical telescope for normal adjustment position. Write down the equation for its magnifying power. (2 marks)
Question 15. The half-life of a radioactive sample is 30 seconds. Calculates (i) the decay constant, and (ii) time taken for the sample to decay to 3/4th of its initial value. (2 marks)
Question 16. Draw a logic circuit diagram showing how a NAND gate can be converted into a NOT gate. (2 marks)
Question 17. What is an ideal diode? Draw the output waveform across R, for the input waveform given below : (2 marks)
Question 18. Write, in brief, the method to determine the distance of an inferior planet from the sun. (2 marks)
Question 19. Explain, with the help of a circuit diagram, the use of potentiometer for determination of internal resistance of a primary cell. Derive the necessary mathematical expression. (3 marks)
Question 20. Calculate the resistance between A and B of the given network. (3 marks)
Question 21. State Faraday's laws of electrolysis. Write down the relation connecting chemical equivalent and electro-chemical equivalent. (3 marks)
Question 22. An electron is moving at 106m/s in a direction parallel to a current of 5 A, flowing through an infinitely long straight wire, separated by a perpendicular distance of 10 cm in air. Calculate the magnitude of the force experienced by the electrons. (3 marks)
Question 23. A bar magnet, held horizontally, is set into angular oscillations in Earth's magnetic field. It has time periods T1 and T2 at two places, where the angles of dip are α1 and α2 respectively. Deduce an expression for the ratio of the resulting magnetic field at the two places. (3 marks)
Question 24. Verify Snell's law of refraction using Huygens' wave theory. (3 marks)
Question 25. Find the position of an object which when placed in front of a concave mirror or focal length 20 cm, produces a virtual image, which is twice the size of the object. (3 marks)
Question 26. If the frequency of the incident radiation on the cathode of a photo cell is doubled, how will the following change:
(i) Kinetic energy of the electrons,
(ii) Photoelectric current,
(iii) Stopping potential.
Justify you answer. (3 marks)
Question 27. Explain, with the help of a circuit diagram, why the output voltage is out of phase with the input voltage in a common emitter transistor amplifier. (3 marks)
Question 28. With the help of a labeled diagram, describe Milliken’s oil-drop experiment for determining the charge of an electron. (5 marks)
Question 29. Draw the curves showing the variation of inductive reactance and capacitive reactance with applied frequency of an a.c source. A capacitor, a resistor of 5 ohm, and an inductor of 50 mH are in series with an a.c. source marked 100 V, 50 Hz. It is found that voltage is in phase with the current. Calculate the capacitance of the capacitor and the impedance of the circuit. (2+3 marks)
Question 30. Define capacitance of a capacitor. Give its unit. Derive an expression for the capacitance of a parallel plate capacitor in which a dielectric medium of dielectric constant K fills the space between the plates.
Or
Explain the principle, construction and working of a Van de Graff generator. (5 marks)
Sample paper 4
XII PHYSICS
Q. 1. In a hydrogen atom, an electron revolves around a proton. Which of these two exerts a greater electrostatic force on the other?
Q. 2. What is the force experienced by a positively charges particle Q moving at right angles to a uniform electric field E.
Q. 3. What is the order of voltages that can be built up using a Van De Graff generator?
Q. 4. What is the angle b/w Electric field and Dipole moment at an axial point?
Q. 5 Define geomagnetic ratio. What is its value?
Q. 6 State the condition in which terminal voltage across a secondary cell is equal to its emf.
Q. 7. The dielectric strength of air is 3 x 106 V/m. What is the maximum charge that can be safely stored on a sphere of radius 10m?
Q. 8. Name two types of commercially available resistors.
Q. 9. On the same graph plot the variation of E versus R and V versus R for a point charge.
Q. 10. Define mobility and mention its SI unit
Q. 11. Two resistors are connected in parallel b/w A and B to give a net resistance of 2 ohms. When one of these resistors is broken, the net resistance becomes a 3 ohms. What is the resistance of the resistor that was broken?
Q. 12. Using a suitable graph, explain why nichrome is used in standard resistance coils.
Q. 13. A velocity selector is to be designed for particles of velocity 10m/s. What magnetic field should be employed if the electric field in it is 100 N/C
Q. 14. Explain why a potentiometer is preferred over a voltmeter for measuring potential differences.
Q. 15. An alpha particle and a proton accelerated by the same potential difference enter into a magnetic field. Find the ratio of their radius and the ratio of their frequency.
Q. 16. In a meter bridge experiment with a fixed resistor of 10 ohm, the balance length is found to be 75cm. What resistance should be added in series with this fixed resistor so as to bring the null point in the center of the wire?
Q. 17. The resistively of a metal X is 3.2 x 10-8 while the free electron density is 5 x 1028 m-3. Find the drift velocity of electrons if a potential gradient of 1 Vm-1 is applied across X.
Q. 18. What type of materials are used for making - Permanent magnets
- Transformer cores. Give two line reasons for each
Q. 19. In the circuit, what is the reading of the voltmeter?
What resistance should be connected in series with the R = 6 ohm resistor so the voltmeter reading become zero
What resistance should be connected in series with the R = 6 ohm resistor so the voltmeter reading become zero
Q. 20. Show that the far field of a solenoid resembles that of a bar magnet. Hence define the magnetic moment of a solenoid.
Q. 21. A long cylinder of radius Ro is carrying a current Io, which is uniformly distributed over its cross section. Derive an expression for the magnitude of magnetic field inside as well as outside the wire. Plot a curve to show the variation of magnetic field with radial distance.
Q. 22. A and B are two concentric hollow metallic shells of radius RA and RB. A is given a charge QA while B is given a charge QB. Find the electric potential at a distance R from the center such that
- R < RA
- RA < R < RB
- R > RB
Q. 23. Derive an expression for the torque acting on a current carrying loop placed in a uniform magnetic field. Hence define the magnetic moment of a current carrying loop.
Q. 24. Use kirchoff’s laws to deduce the condition of a balanced Wheatstone bridge.
Q. 25. Explain mathematically, why the resistance of metals increases while that of semiconductor decreases with the rise in temperature. Plot Resistance versus Temperature for Cu and for Silicon.
Q. 26. Three charges Q , Q and – Q are placed on the vertices of an equilateral triangle of side L. Find the net force experienced by the charge Q and the net force experienced by the charge – Q.
Q. 27. Cell A has an emf EA and internal resistance rA while cell B has emf EB and internal resistance rB. Derive an expression for the equivalent emf and internal resistance
Q. 28. Using a labeled diagram explain the construction and working of a moving coil galvanometer. Define its current and voltage sensitivity and explain how they can be increased.
(b) A galvanometer with a coil resistance of 5 ohm can tolerate a maximum current of 10mA. Explain how this can be converted into an ammeter of range 1A.
(b) A galvanometer with a coil resistance of 5 ohm can tolerate a maximum current of 10mA. Explain how this can be converted into an ammeter of range 1A.
Q. 29. There are a total of N cells each of emf E and internal resistance r. They are connected in the form of a 2 dimensional array of “n” rows each having equal number of cells. What is the maximum current that can be obtained from this combination?
(b) This array is connected to an external resistor R. Derive an expression for the current flowing through R. For what value of R is this current maximum.
(b) This array is connected to an external resistor R. Derive an expression for the current flowing through R. For what value of R is this current maximum.
Q. 30. Derive the value of potential due to an electric dipole at a point r distance away at an angle θ. On same graph show the variation of potential with distance for a point charge and for a dipole
Sample Paper – 2011
Class – XII
Subject – Physics
COMMON MISTAKES COMMITTED BY THE STUDENTS IN JNVs IN PHYSICS OF CLASS XII
Class – XII
Subject – Physics
COMMON MISTAKES COMMITTED BY THE STUDENTS IN JNVs IN PHYSICS OF CLASS XII
The following area / contents are being given below which are generally some confusable / mistakable for the students in Physics Subject for XII Class syllabus.
UNIT No. 1: ELECTROSTATICS:-
i) Electric field intensity & Electric Potential due to electric dipole.
ii) Way for finding the directions of Electric field.
iii) Effect of dielectric in capacitors.
iv) Numeric Problems based on counter nation of capacitors.
v) Area Vector concept in Gauss Theorem.
UNIT 2: CURRENT ELECTRICITY
i) Factors affecting the resistance of a register (conductor) i.e. Relaxation time Temp. etc.
ii) Circuit diagram (Wheatstone Bridge , Meter Bridge
iii) Numerical on Wheatstone Bridge , Meter Bridge
iv) Combination of resistances
UNIT 3: MAGNETIC EFFECT OF CURRENT
i) Direction of magnetic field in different situation
ii) Biota Savant Law ( Formula in vector form )
iii) Sensitivity of Galvanometer.
iv) Magnetic dipole moment & Electric dipole moment.
v) Die & Para magnetic substances.
UNIT 4: E.M.I. & A.C.
i) Applications of Lentz Law
ii) Instantaneous, Peak & r m s. value of AC current / voltage.
iii) AC through pure inductor & capacitor phase difference between voltage & current
iv) Numerical Problems based on LCR series circuit ( condition of resonance )
v) Power factor.
UNIT 5: E.M.WAVES
i) Conditions of propagation of E.M. Waves
i) Numerical Problem based on lens formula.
ii) Resolving power; magnifying power of optical instruments.
iii) Conditions of Interference & Diffraction
iv) Single slit diffraction pattern.
v) Huygens’s wave theory explanation for Reflection & Refraction Laws.
UNIT 7: DUAL NATURE OF MATTER & RADIATION
i) Explanation of laws of Photo Electric Effect using Einstein equation
ii) Derision & Germen Experiment (Polar Graphs)
UNIT 8: ATOMIC NUCLEUS
i) Decay law
ii) Explanation of Binding Energy curve & numerical problems based on B.E. per nucleus
UNIT 9: SOLID & SEMI CONDUCTOR DEVICES
i) Energy level diagram for Extrinsic & intrinsic semiconductors
ii) Biasing of P-N Junction diode
iii) Transistors PNP & NPN Biasing
iv) Applications of Logic gates.
UNIT 10: PRINCIPLES OF COMMUNICATION
i) Block diagram of transmission and reception system
ii) Wave shape of analog and digital signals
iii) Wave shape of frequency & amplitude modulated wave for sine and square wave
Electrostatics
| S. No. | CONTENT AREA | QUESTIONS |
| 1 | Electrostatics Charges | 1. A glass rod rubbed with silk acquired a charge + 1.6x10-14c. What is the charge on the silk? 2. What is quantization of charge? 3. State Coulombs Law. Write its 4. Define dielectric constant of a medium. Dielectric constant of a medium is unity, What will be its permittivity? 5. Force between two point charges Kept at a distance γ apart in air is F. If these charges are kept in the water at the same distance how does the force between them |
| 2 | Electrostatic Field | 1. Draw electric lines of force due to i) an isolated positive point charge (q>o) ii) an isolated negative point charge (q>o) 2. Two electric lines of force do not interact. Explain why? 3. Define the term electric dipole moment. 4. Give two properties of electric lines of force. Sketch them for a positively charged metallic sphere. 5. Desire an expression for electric field intensity at a distance ‘r’ from a point charge “q”. 6. State Gauss Theorem in electrostatics. Give its mathematical form. 7. Two point charges +e and +VE coulomb are separated by a distance of 6r. Find the point on the line joining the two charges where the electric field is zero. 8. State Gauss theorem in electrostatics. Apply this theorem to calculate the electric field due to an infinite plane sheet of charge. 9. An electric dipole is held in a uniform electric field i) Show that no translator force acts on it ii) Derive an expression or the torque acting on it . 10. Define the term Electric flux. What is its S.I. Unit? An electric flux of -6x103 Nm2/c passes normally through a spherical Gaussian surface of radius 10 cm, due to point charge placed at the centre. a) What is the charge enclosed bye the Gaussian surface? b) If the radius of the Gaussian surface is doubled, how much flux would pass through the surface. 11. Derive an expression for the total work done in rotating an electric dipole through an angle O is a uniform electric field E. 12. Derive an expression for the electric field intensity at any point along the axial line of an electric dipole. |
| 3. | Electric Potential Electric Potential Energy | 1. Calculate the work done in moving a charge of 10-6 coulomb, 5cm on an equipotent surface. 2. Show that E = -dv / dr 3. (i) Calculate the electric potential at a point P due to charge of 0.5 μ c located at 10 cm from it . (ii) Also calculate the work done in bringing a charge of 3x10-9 c from infinity to point p. 4. Derive an expression for the potential at a point along the axial line of a short electric dipole. 5. Define “electric potential”. Deduce an expression for the electric potential at a point distance ‘r’ form a point charge ( 7°) 6. Explain the concept of Electric potential energy. Derive an expression for the potential energy of a sys teem of two point charges 7. A proton is moved in a uniform electric field of 1.7 x 10-4 N/c between two point A and B separated by a distance of 0.1m. (i) What is the potential difference between the oats? (ii) How much work is done in above process? |
| 4. | Capacitance Capacitors Grouping of Capacitors Van – de – Graft Generator | 1. Define capacitance of a capacitor? 2. How id dielectric constant expressed in terms of capacitance of a capacitor? 3. Two protons p1 and p2 are place between two parallel plates having a potential difference V as shown in the figure. Will these protons experience equal or unequal force? + - + p1 - + - + - + p2 - 4. Name the physical quantity whose S.I. unit is (i) coulomb/volt (ii) Joule /coulomb. 5. Derive an expression for the energy stored in a capacitor. 6. How much energy will be stored in a capacitor of 100 μF capacity, when charged by a battery of 20v? 7. Three capacitors of equal capacitance, when connected in series, have a net capacitance of C1 and when connected in parallel have a capacitance of c2. What will be the value of C1/C2. 8. Explain the principal of a Capacitor. 9. Obtain equivalence capacitance of the following network given C1 = C4 = 100pF C2 = C3 = 200pF 10. Dielectric slab of thickness t is introduced between the plates of a parallel plate capacitor, separated by a distance (t<d). Derive an expression for the capacitance of the capacitor? A capacitor of 20μFand charged to 500v is connected in parallel with another capacitor of 10μF charged to 200v. Find the common potential 12. Define capacitance of a capacitor. Give it S.I. Unit. Prove that the total electrostatic energy stored in a parallel plate capacitor is 1-2 CV2. Hence derive the expression for energy density of a capacitor. |
| 6 | Electric current Resistance & E.M.F. | 1. What is the S.I. Unit of electric current? 2Are the direction of conventional and electric current same? 3. What is the cause of resistance of a conductor? 4. Define resistivety. Give its S.I. Unit 5. Define potential gradient of a wire. Give its S.I. Unit. 6. What is the effect of temperature on the conductivity of electrolyte? 7. A carbon resistor is marked in colored bands of red, black, orange, and silver, what is its resistance with tolerance? 8 What are the factors on which the resistance oaf material depends? Give the corresponding relation. 9. What is the thermostat? Give its two applications 10. State Kickoffs laws for an electrical network? 11. What is super conductivity? Write its two applications. 12. Define resistively of a conductor and state its S.I. Unit. State and explain how the resistively of a conductor varies with temperature. 13. Derive an expression for the drift speed of electrons in a good conductor in terms of relaxation time of electrons. 14. Define the terms resistively of a conductor. Give its S.I. Unit. Show the resistance R of a conductor is given by ml/ ne2T. Where symbols have their usual meaning. 15. V – I graph for a metallic wire at two different temperatures T1 and T2 is as shown in the following figure. which of the two temperatures is higher and why T1 I T2 V |
| 7. | Electrical Measurement | 1. Why potentiometer is preferred over volt meter for measuring potential d |
ACTION PLAN FOR XII (PHYSICS)
HOW TO IMPROVE PERFORMANCE OF BRIGHT CHILDREN
1. Identification of Bright students.
2. Study Material prepared by the teachers, some special reference book and advanced study material should be provided to them.
3. Extra Assignment and High Standard question on CBSE pattern should be given to the students.
4. Bright children must be motivated to go through each and every line of the NCERT Text book. They should be motivated to solve the exercises of NCERT Book.
5. More and more stress on solving Numerical Problems.
6. Application and Understanding based questions related to different theorem and fundamental principles should be given. Different questions from previous 5 years (at least) CBSE papers and from different sample papers should also be described.
7. Students should be made aware about the word limit for answering the questions.
8. Students should concentrate only on CBSE Exams avoiding preparation for other competitive exams.
9. Time Management is also compulsory.
10. All the topics of the CBSE Curriculum must be thoroughly studied.
11. To make aware the students about the marking scheme of Board Exams, they can understand the tricks for scoring good marks.
12. Some special practice set prepared by the teachers should be provided to bright students continuously. After evaluation students should make aware about the mistakes made by them.
13. At least continuous motivation and encouragement and continuous guidance of subject expert to the students.
COMMON ERRORS COMMITTED BY THE STUDENTS
(CLASS- XII)
1. After solving the numerical problems don’t write SI-Units of the Physical Quantities.
2. Before attempting the Numerical convert all the given Physical Quantities in SI-Units.
3. The answer should be the point.
4. Show ray direction in ray-diagrams & current direction in circuit diagrams.
5. Clearly not show the Polarized & unpolarized Light.
6. Not aware while drawing a resistance & capacitor in circuit diagrams.
7. Not aware while drawing a resistance & inductor in circuit diagrams.
8. Generally don’t write the name of Physical Quantities used in the formula.
9. Not differentiate between Faraday’s Law of EM-Induction & Faraday’s Laws of Electronics.
DIFFICULT AREAS AND QUESTION BASED ON THE TOPICS CLASS XII
| UNITS | TOPIC | QUESTION |
| 1. Electro Statics 2. Current Electricity | (a) Gauss Theorem (b) Electric Dipole (c) Capacitor (a) Kirchhoff’ s Law (b) Dependence of Resistively | (1) Explanation of Gauss Theorem & Its applications for plane Conducting sheets. (2) Electric field intensity due to a short dipole at its equation point Axial points. (3) Effect of conducting & Dielectric slab between plates of a parallel plate capacitor. (1)Numerical based on Law. (2)Calculation of current & charge stored in a capacitor & resistance mixed circuit. (1) Dependence of Resistively on temperature & Relaxation time and its explanation. |
| 3.Magnetic Effect of current & Magnetism | a) Magnetic field b) Galvanometer c) Magnet | 1) Magnetic field at the axis of current carrying circular coil 1) Conversion of Galvanometer into ammeter & voltmeter of desire range. 1) Explanation of mega meridian & Geographic meridian , angle or dip |
| 4. E.M.I. & A.C. | a) Pharos diagrams b) Power factor c) Resonance | 1) Expression for LCR – Circuit by pharos diagrams & numerical based on resonant condition 1) Derivation of power factor for LCR – Circuit. 1) Numerical based on ע – 1/(2Π√LC) resonance condition |
| 5. E.M. Waves | a) Transverse Nature | 1) Expression & Explanation of Transverse Nature of EM – Waves |
| 6. Optics | a) Wave front b) Refraction c) Lens makers formula d) Diffraction e) Resolving power | 1) Concept of wave front & its classification & Explanation. 1) Explanation of Refraction on the basis of wave theory. 1) Derivation of Lens makers Formula with labeled diagram. 1) Diffraction due to a single slit & explanation for central maxima & minima 1) Resolving power of microscope & Telescope | 2 3 5 3 2 |
| 7. Dual Nature of Matter & Radiation | a) Davison German Experiment b) Photo – Electric effect | 1) Explanation of D. & G. Experiment. 1) Explanation of Einstein’s Photo electric equation | 3 3 |
| 8. Atomic Nucleus | a) Half life b) Binding energy (c) α -Scattering Experiment | 1) Calculation of Binding Energy per nuclei for given nuclear Reaction. (ΔE = Δmc2) (1) Explanation of α -Particles scattering. | 3 3 |
| 9. Solid & Semiconductor Devices | (a) PN-Junction Diode (b) Transistor | (1) Formation of Depletion Layer in forward & reverse biasing of a PN-Junction diode. (1) Zever Diode as a voltage regulator & its curve. (1)Input & Output characteristics curve of NPN & PNP- Transistor. (2) Transistor as oscillator. | 3 3 3 3 |
| 10. Principles of Communication | (a) Demodulation (b) Block Diagrams | (1) Concept of Demodulation. (1) Explanation of Receiver & Transmitter on the basis of Block Diagrams. . | 2 3 |
Unit –8 (Atomic Nucleus)
Questions for slow learners students.
1. Give Bohr Model of atom & it ‘s Hypothesis?
2. Determine value of velocity, radius, time period, Energy of a atom with the help of Bohr Model?
3. Why cadmium Rod is used in Nuclear reactors?
4. Why is Heavy water used in Nuclear Reactors?
5. Define fission reaction & Fusion reaction?
6. Give an example of Fission reaction & Fusion reaction?
7. Give relation between mass in amu with kg
8. Give the relation b/w Joule & eV energy.
9. Define half life of Radio active decay.
10. Define Radio activity?
11. Explain α decay with an example & what effect on parent nuclei when α particle decay?
12. Explain β -, β +, β0 decay with an example of each? What effect on parent nuclei when β -, β +, β 0 particles decays from Nucleus?
13. Identify D2
235 β α
D D1 D2 92
18. Identify D4
235 α β α β
D D1 D2 D3 D4 92
19. Write the S1 unit for the activity of a Radioactive decay?
20. Write β decay in the Nuclear decay process .
21. Unit –9 (Solid and Semi conductor devices)
Questions for slow learners students.
1. What type of charge carriers are there in an n type semiconductor and p type semiconductor.
2. Which type of biasing results in very high resistance of a P n Junction?
3. Write down the truth table of AND, OR, NOT, NAND and NOR gate.
4. Why a common emitter is generally preferred over a common base amplifier.
5. Is the Diode D forward or reverse biased in the given diagram?
6. Draw energy band diagram of n type and p type semiconductor.
7. With the help of circuit diagram explain the working principle of a full wave Testifier.
8. Draw energy band diagram of metal, Insulator and Semiconductor.
9. For a transistor connected in common emitter mode, the voltage drop across the collector is 1.5 v and base is 50. Find the base current if Rc is 1.5 k.\
10. What is the magnitude of potential barrier for (a) Ge Junction (b) Si Junction
11. Explain zener diode.
12. What is an intrinsic semi conductor? Why does its conductivity increase with rise of Temperature?
13. What is an N-P-N transistor? How does it differ from P-N-P transistor? Give their symbols. Explain it action.
14. Explain through a labeled circuit diagram the working of a transistor as amplifier (common emitter configuration)
15. Explain through a labeled circuit diagram, the working of a transistor as an oscillator.
16. Explain transistor as a switch with circuit diagram.
17. The input resistance of a common emitter amplifier is 2k and a c. current gain is 20. If the load resister used is 5k , calculate (i) the voltage gain of the amplifier. (ii) The Trans conductance of the transistor used.
18. Draw a circuit diagram for a two input or and AND gate and explain its working with the help of Input and output wave form.
Unit –10 (Principle of communication)
Questions for slow learners students.
1. Distinguish between analog signal and digital signal.
2. What is modulation?
3. What is the various method of modulation?
4. Define modulation factor.
5. What is amplitude modulation?
6. Show graphically amplitude modulation.
7. What are the limitations of amplitude modulation?
8. What is the importance of modulation index?
9. Draw a sketch to illustrate the basic elements required to transmit and receive an audio signal.
10. Why do we need modulation?
11. It is necessary to use satellites for long distance T.V. Transmission. Give one reason.
12. Derive the height of antenna h up to which the T.V. signal can be directly received from a T.V.
13. Explain amplitude modulation. How is it modulated & detected.
Unit – 7 (Dual Nature of Matter & Radiations)
1. Define Threshold frequency.
2. Define work function of a metal.
3. Draw the graph showing the variation of stopping potential & frequency.
4. Derive the relation for the De-Brule’s wave-length for the matter particles.
5. An electron & a proton are possessing same K.E. which of the two has greater De-broglie wavelength.
6. The freq. of light incident on the surface of a metal in doubled keeping the intensity same. What is the effect on – (i) K.E. of photo electrons. (ii) Photo electric potential. (iii) Stopping potential. Justify the answer in each case.
7. Derive the wavelength for an electron.
8. What is Einstein’s photo electric equation? With the help of this equation. Explain the photo electric effect laws?
9. What are photo electric effect laws?
10. Explain the wave nature of electron with the help of Deviation & Garner experiment.
Ajay Sharma
9414368091
E-mail- aks.672@rediffmail.com
