CLASS XII: PHYSICS

ASSIGNMENT / PRACTICE SHEET-1

Q-1) Why do the electric field lines never cross each other?

Q-2) Can a charged body attract another uncharged body? Explain.

Q-3) A 500μC charge is at the centre of a square of side 10 cm. Find the work done in

moving a charge of 10μC between two diagonally opposite points on a square.

Q-4) What is meant by capacitance? Give its SI unit.

Q-5) Sketch a graph to show how charge Q given to a capacitor of capacitance C varies

with the potential difference V.

Q-6) Sketch a graph showing variation of resistivity of Carbon with temperature.

Q-7) A wire of ‘resistivity’ ρis stretched to twice its length. What will be its new

resistivity?

Q-8) Write the condition under which the potential difference between the terminals of

a battery and its emf are equal.

Q-9) A carbon resistor has colour code as blue, yellow and red respectively. What will be

the resistance?

Q-10) Why is it easier to start a car engine on a warm day than on a chilly day?

Q-11) Estimate the average drift speed of conduction electrons in a copper wire of cross

sectional area 2.5 X 10-7m2 carrying a current of 2.7A. Assume the density of conduction

electrons to be 9 X 1028m-3 .

Q-12) Two point charges qA = +3μC and qB = -3 μC are located 20 cm apart in vaccum.

(i) Find the electric field at the mid-point of the line AB joining the two charges.

(ii) If a negative test charge of magnitude 1.5 X 10-9C is placed at the centre, find the

force experienced by the test charge.

Q-13) State Gauss’s law in electrostatics. Use this law to derive an expression for the electric

field due to an infinitely long straight wire of linear charge density λ cm-1.

+

300V

-

100 pF

200 pF 200 pF

C2 100 pF C3

C4

C1

Q-14) Two dielectric slabs of dielectric constants k1 and k2

are filled in between the two plates each of area A, of the

parallel plate capacitor as shown in the figure. Find the net capacitance of the capacitor.

Q-15) Two point charges 4Q,Q are separated by 1m in the air. At what point on the line

joining the charges is the electric field intensity zero? Also, calculate the electrostatic

potential energy of the system of charges ,taking the value of charge , Q = 2 X 10-7 C.

Q-16) Obtain the equivalent capacitance of the network in fig. For a

300V supply, determine the charge and voltage across each capacitor.

Q-17) State the principle of potentiometer. Draw a circuit diagram

used to compare the emf of two primary cells. Write the formula used.

How can the sensitivity of a potentiometer be increased?

Q-18) Determine the current in each branch of network shown in

figure.

K1 l/2 K2 l/2

A A

5Ω

C

D

B

5Ω

5Ω

10Ω

10Ω

10Ω

10V

C

CLASS XII: PHYSICS

ASSIGNMENT / PRACTICE SHEET-2

Q-1) An electron does not suffer any deflection while passing through a region of

uniform magnetic field. What is the direction of the magnetic field?

Q-2) An electron is moving along +ve x-axis in the presence of uniform magnetic field

along +ve y-axis. What is the direction of force acting on it?

Q-3) Define magnetic flux . Give its SI unit.

Q-4) An electron moving through a magnetic field does not experience any force. Under

what condition is this possible?

Q-5) What is shunt? State its SI unit.

Q-6) What is the nature of magnetic field in a moving coil galvanometer?

Q-7) Write the SI unit of (i) magnetic pole strength (ii) magnetic dipole moment of bar

magnet

Q-8) Give two factors by which the current sensitivity/voltage sensitivity of a moving coil

galvanometer can be increased.

Q-9) The ratio of the horizontal component to the resultant magnetic field of earth at a

given place is 1

2 . What is the angle of dip at that place?

Q-10) The vertical component of earth’s magnetic field at a place is 3 𝑡𝑖𝑚𝑒𝑠 the

horizontal component. What is the value of angle of dip at this place?

Q-11) What is the value of the horizontal component of the earth’s magnetic field at

magnetic poles?

Q-12) Horizontal and vertical components of earth’s magnetic field at a place are 0.22 T

and 0.38 T respectively. Find the resultant intensity of earth’s magnetic field.

Q-13) What should be the orientation of a magnetic dipole in a uniform magnetic field

so that its potential energy is maximum.

Q-14) What is the angle of dip at a place where horizontal and vertical components of

earth’s field are equal?

Q-15) How does the magnetic susceptibility of a paramagnetic material change with

temperature?

Q-16) Name the parameters needed to completely specify the earth’s magnetic field at a

point on the earth’s surface?

Q-17) What is the effect on the magnetization of a diamagnetic substance when it is

cooled?

Q-18) Why electromagnets are made of soft iron?

Q-19) Explain principle, construction and working of a cyclotron.

Q-20) Explain working and principle of a moving coil galvanometer. How it is being

converted into an ammeter and voltmeter. Give mathematical expression.

Q-21) (i) Derive the expression for magnetic field due to circular loop at axial point.

(ii) Derive an expression for the torque acting on a loop of N turns, area A, carrying

current I, when held in a uniform magnetic field.

Q-22) Distinguish among diamagnetic, paramagnetic and ferromagnetic materials in

respect of their (i) intensity of magnetization, (ii) behaviour in a non uniform

magnetic field and (iii) susceptibility.

Q-23) An electron moves around the nucleus in a hydrogen atom of radius 0.51 Å, with a

velocity of 2 x 105 m/s. Calculate the following:

(i) the equivalent current due to orbital motion of electron,

(ii) the magnetic field produced at the centre of the nucleus

(iii) the magnetic moment associated with the electron.

CLASS XII: PHYSICS

ASSIGNMENT / PRACTICE SHEET-3

Q-1) Define magnetic flux. Give its SI unit.

Q-2) Two identical loops , one of copper and another of constantan are removed from a

magnetic field within the same time interval. In ehich loop wil the induced current

be greater?

Q-3) Self inductance of an air core inductor increases from 0.01mH to 10mH on

introducing an iron core into it. What is the relative permeability of the core used?

Q-4) Define one henry.

Q-5) When current in a coil changes with time , how is the back emf induced in the coil

related to it?

Q-6) What do you mean by power factor? On what factors does it depend?

Q-7) When a lamp is connected to an alternating voltage supply, if lights with the same

brightness as when connected to a 12 V DC battery. What is the peak value of

alternating voltage source?

Q-8) Find the capacitance of the capacitor that have a resistance of 100Ω when used

with an a.c. source of frequency 5/𝜋 kHz.

Q-9) The power factor of an a.c. circuit is 0.5. What will be the phase difference between

voltage and current in this circuit?

Q-10) What happens to the power dissipation if the value of electric current passing

through a conductor of constant resistance is doubled?

Q-11) Why is the use of a.c. voltage preferred over d.c. voltage? Give two reasons.

Q-12) To which part of the electromagnetic spectrum does a wave of frequency 5 X 1011

Hz belong?

Q-13) Write the functions of following in communication systems: (i) Reciever (ii)

Demodulator

Q-14) Name the EM waves used for studying crystals structure of solids. What is its

frequency range?

Q-15) Name the part of electromagnetic spectrum which is suitable for (i) radar systems

(ii) treatment of cancer tumours.

Q-16) Write any two applications of X-rays.

Q-17) Write any four characteristics of electromagnetic waves.

Q-18) A bulb and a capacitor are connected in series to an a.c. source of variable

frequency. How will the brightness of the bulb change on increasing the frequency

of the a.c. source? Give reason.

Q-19) What is iron loss in a transformer?

Q-20) What is eddycurrents? Write its applications.

Q-21) Explain principle construction and working of an A.C. generator.

Q-22) An inductor 200 μH, capacitor 500 μF, resistor 10 Ω are connected in series with a

100 V , variable frequency a.c source. Calculate the

(i) Frequency at which the power factor of the circuit is unity.

(ii) Current amplitude at this frequency

(iii) Q-factor

Q-23) What is transformer? Show that, in ideal transformer , when the voltage is

stepped up a by a certain factor , the current gets stepped down by the same factor.

State any two causes of energy loss in transformer.

Q-24) A voltage V = V0 sin 𝜔t is applied to a series LCR circuit. Derive the expression for

the average power dissipated over a cycle. Under what condition is (i) no power

dissipated even though the current flows through the circuit , (ii) maximum power

dissipated in the circuit.

CLASS XII: PHYSICS

ASSIGNMENT / PRACTICE SHEET-4

Q-1) Two thin lenses of power +4D and -2D are in contact. What is the focal length of

the combination?

Q-2) What is presbyopia? How can it be corrected?

Q-3) A converging lens of refractive index 1.5 is placed in a trough of liquid. What must

be the refractive index of the liquid in order to mark the the lens disappear?

Q-4) How does the power of a convex lens vary, if the incident red light replaced by

violet light?

Q-5) How does the angle of minimum deviation of a glass prism of refractive index 1.5

change, if it is immersed in a liquid of refractive index 1.3?

Q-6) Write the necessary conditions, for the phenomenon of total internal reflection to

take place?

Q-7) A lens of glass is immersed in water. What will be its effect on the power of the

lens?

Q-8) Why is convex mirror used as driver’s mirror?

Q-9) A ray of light falls on a mirror normally. What are the values of angle of incidence

and angle of reflection.

Q-10) What is the number of images of an object held between two parallel plane

mirrors?

Q-11) How would the angular separation of interference fringes in Young’s double slit

experiment change when the distance between the slits and and screen is halved?

Q-12) What is the value of refractive index of a medium of polarizing angle 60°.

Q-13) If the angle between the pass axis of polarizer and the analyser is 45°, write the

ratio of the intensities of original light and the transmitted light after passing

through the analyser.

Q-14) The monochromatic source of light in Young’s double slit experiment is replaced

by another monochromatic source of shorter wavelength. What will be the effect?

Q-15) Why cannot we obtain interference using two independent sources of light?

Q-16) Is the speed of light in glass independent of the colour of light?

Q-17) The phase difference between two waves reaching a point is 𝜋/2. What is the

resultant amplitude, if the individual amplitudes are 3mm and 4mm.

Q-18) What is the ratio of slit widths when amplitudes light waves from them have a

ratio 2: 1.

Q-19) Which three phenomenon establish the wave nature of the light?

Q-20) How does the resolving power of microscope change on (i) decreasing wavelength

of light , (ii) decreasing diameter of objective lens.

Q-21) A convex lens of focal length 20cm is placed coaxially with a convex mirror of

radius of curvature 20 cm. The two are kept 15 cm apart. A point object is placed

40cm in front of the convex lens. Find the position of the image formed by this

combination. Draw the ray diagram showing the image formation.

Q-22) (i) Draw a ray diagram of a compound microscope. Write the expression for its

magnifying power.

(ii) Draw a ray diagram of an astronomical telescope in the near point adjustment.

Write down expression for its magnifying power.

Q-23) In a Young’s double slit experiment , describe briefly how bright and dark fringes

are obtained on the screen kept in front of a double slit. Hence obtain the

expression for the fringe width.

Q-24) (a) Show , giving a suitable diagram , how unpolarized light can be polarized by

reflection.

(b) Two polaroids P1 and P2 are placed with their pass axes perpendicular to each

other. Unpolarized light of intensity I0 is incident on P1. A third Polaroid P3 is kept

in between P1 and P2 such that the pass axis makes an angle of 60° with that of P1.

Determine the intensity of light transmitted through P1 , P2 and P3.

CLASS XII: PHYSICS

ASSIGNMENT / PRACTICE SHEET-5

Q-1) An electron and alpha particle have the same de-Broglie wavelength associated

with them. How are their kinetic energies related to each other?

Q-2) How does the stopping potential applied to a photocell change, if the distance

between the light source and the cathode of the cell is doubled?

Q-3) de-Broglie wavelength associated with an electron accelerated through a potential

difference V is λ. What will be its wavelength when the accelerating potential is

increased to 4 V?

Q-4) Two metals A and B have work function 2 eV and 5eV respectively. Which metal has

lower threshold wavelength?

Q-5) Ultraviolet light is incident on two photosensitive materials having work functions

W1 and W2 (W1 > W2) . In which case will the kinetic energy of the emitted electrons

be greater? Why?

Q-6) The frequency (v) of the incident radiation is greater than the threshold frequency

(v0) in a photocell. How will the stopping potential vary if v is increased , keeping

other factors constant?

Q-7) Show graphically how the stopping potential for a given photosensitive surface

varies with the frequency of the incident radiation?

Q-8) Plot a graph showing the variation of photoelectric current with anode potential for

two light beam of same wavelength but different intensity?

Q-9) An electron , an alpha particle and a proton have the same kinetic energy. Which

one of these particles has the largest de-Broglie wavelength?

Q-10) What is the difference between thermionic emission and photoelectric emission?

Q-11) In a Rutherford’s 𝛼-scattering experiment with thin gold foil , 8100 scintillations

per minute are observed at an angle of 60°. What will be the number of

scintillations per minute at an angle of 120°?

Q-12) Name the series of hydrogen spectrum lying in the infrared region.

Q-13) The shortest wavelength in the Lyman series is 911.6 Å. Then the longest

wavelength in the Lyman series is :

Q-14) Two nuclei have the mass numbers in the ratio 27:125. What is the ratio of their

nuclear radii?

Q-15) The radioactive isotope D decays according to the sequence. 𝛽− 𝛼 − 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒

D D1 D2

If the mass number and atomic number of D2 are 176 and 71 respectively, what is

the (i) the mass number (ii) the atomic number of D

Q-16) Draw a graph showing the distribution of kinetic energy of electrons emitted

during beta decay.

Q-17) What is the nuclear radius of Fe125 , if that of Al27 is 3.6 fermi?

Q-18) Name the reaction which takes place when a slow neutron beam strikes 𝑈92235

nuclei. Write the nuclear reaction involved.

Q-19) ‘Heavy water is often used as a moderator in thermal nuclear reaction’? Give

reason.

Q-20) A nucleus n𝑋𝑚 emits one alpha particle and one beta particle. Find the mass

number and atomic number of the product nucleus.

Q-21) For what kinetic energy of a proton , will the associated de-Broglie wavelength be

16.5 nm?

Q-22) The ground state energy of a hydrogen atom is -13.6 eV. (i) What is the potential

energy of an electron in the 3rd excited state? (ii) If the electron jumps to the

ground state from the third excited state , calculate the wavelength of the photon

emitted.

Q-23) The half life of 𝑆𝑟3890 is 28 years. What is the disintegration rate of 15 mg of this

isotope?

Q-24) Define half-life (T1/2) and average life (𝜏) . Derive a relation between these two.

CLASS XII: PHYSICS

ASSIGNMENT / PRACTICE SHEET-6 TOPICS:

Q-1) Give the logic symbol of AND gate.

Q-2) Why should a photodiode be operated at a reverse bias?

Q-3) State the factor , which controls:

(i) Wavelength of light and (ii) intensity of light emitted by an LCD.

Q-4) At what temperature would an intrinsic semiconductor behave like a perfect

insulator.

Q-5) Name the type of biasing of a p-n junction diode so that the junction offers very

high resistance?

Q-6) A transistor has a current gain of 50. In a CE amplifier circuit, the collector

resistance is chosen as 5 kilo ohms and the input resistance is 1 kilo ohm. Calculate

the output voltage if input voltage is 0.01V.

Q-7) Name an impurity each , which when added to pure Si, produces (i) n-type and (ii)

p-type semiconductor.

Q-8) Name two factors on which electrical conductivity of a pure semiconductor at a

given temperature depends.

Q-9) Why is the conductivity of n-type semiconductor greater than that of the p-type

semiconductor even when both of these have same level of doping?

Q-10) How does the d.c current gain of a transistor change , if the width of the base

region is increased?

Q-11) The a.c current gain of a transistor is 120. What is the change in the collector

current in the transistor whose base current changes by 100 μA?

Q-12) In a p-n transistor circuit the collector current is 10mA. If 90% of the electrons

emitted reach to the collector, find the base current and emitter current.

Q-13) What is doping?

Q-14) In a transistor, current gain for common base and common emitter configurations

are α and β respectively. What is the relation between α and β?

Q-15) Why is NAND (or NOR) gate called a digital building block (or universal gates)?

Q-16) What is space wave propagation?

Q-17) What is the meaning of term ‘attenuation’ in communication system>

Q-18) What are three basic units of communication system?

Q-19) What is the purpose of modulating a signal in transmission?

Q-20) What should be the length of the dipole antenna for a carrier wave of frequency

3 X 108 Hz?

Q-21) It is necessary to use satellites for long distance TV transmission. Why?

Q-22) How does the effective power radiated by an antenna vary with wavelength?

Q-23) Explain the process of amplitude modulation. Draw a schematic sketch showing

how amplitude modulated signal is obtained by superposing a modulating signal over a

sinusoidal carrier wave.

Q-24) (a) State briefly the processes involved in the formation of p-n junction explaining

clearly how the depletion region is formed?

(b) Using the necessary circuit diagrams, show how the V-I characteristics of a p-n

junction are obtained in

(i) Forward biasing (ii) Reverse biasing

How are these characteristics made use of in rectification?

Q-25) (a) Differentiate between three segments of a transistor on the basis of their size

and level of doping.

(b) How is a transistor biased to be in active state?

(c) With the help of necessary circuit diagram, describe briefly how n-p-n

transistor in CE configuration amplifies a small sinusoidal input voltage. Write

the expression for the ac current gain.