CBSE practice Questions

# CBSE Physics Previous Years Paper Board [PDF] ### (Year 2003)

1 Mark Questions:

Question: Define electrical conductivity of a conductor and give its S.I. unit.
Question: What happens to the power dissipation if the value of electric current passing through a conductor of constant resistance is doubled?
Question: How does the (i) pole strength and (ii) magnetic moment of each part of a bar magnet change if it is cut into two equal pieces transverse to its length?
Question: Write S.I. unit of magnetic flux. Is it a scalar or a vector quantity?
Question: Name the factor which decides the quality of reproduced document sent by Fax.
Question: Mention any two properties of electric lines of force. Sketch them for an isolated positive point charge.

Question: An a.c. voltage E = E0 sin cot is applied across an inductor L. Obtain an expression for current I.

### 2 Marks Questions:

Question: Draw a labelled diagram of Van de Graff generator. State its principle of working.
Question: What is meant by ‘drift velocity of free electrons’? Derive Ohm’s law on the basis of the theory of electron drift.
Question: What is Wheatstone bridge? Deduce the condition for which Wheatstone bridge is balanced.
Question: Two straight, parallel, current carrying conductors are kept at a distance ‘r’ from each other, in air. The direction of current in both the conductors is the same. Find the magnitude and direction of the force between them. Hence define one ampere.
Question: Distinguish between diamagnetic and ferromagnetic materials in respect of their (i) intensity of magnetisation, (ii) behaviour in a non-uniform magnetic field and (iii) susceptibility.

### 3 Marks Questions:

Question: State Huygens’ principle. For reflection of a plane wave front at a plane reflecting surface, construct the corresponding reflected wave front. Using this diagram, prove that angle of incidence is equal to angle of reflection.
Question: What is meant by interference of light?
In a double slit experiment with monochromatic light, fringes are obtained on a screen placed at some distance from the slits. If the screen is moved by 5 x 10 -2 m towards the slits, the change in fringe width is 3x 10 -5 m. If the distance between slits is 10 -3 , calculate the wavelength of light used.
Question: Define Antenna. Write a short note or Antenna. Name two types of antenna.
Question: What is meant by the term ‘modulation’? Explain with the help of a block diagram, how the process of modulation is carried out in radio broadcasts.
Question: Write three special characteristics of the light source used in optical communication. Name any one optical detector. Explain the meaning of the term ‘sensitivity’ and ‘responsivity’ of a detector.
Question: Draw a ray diagram to show the formation of image of an object placed between the optical centre and focus of the convex lens. Write the characteristics of image formed. Using this diagram, derive the relation between object distance, image distance and focal length of the convex lens. Write the assumptions and convention of signs used.

5 Marks Questions:

Question: Draw a circuit diagram of a common emitter amplifier using n-p-n transistor. Show input and output voltages graphically.
The current gain for common emitter amplifier is 59. If the emitter current is 6.0 mA, find (i) base current and (ii) collector current.

### (Year 2004)

1 Mark Questions:

Question: Name the type of modulation scheme preferred for digital communication.
Question: What is the name given to that part of electromagnetic spectrum which is used for taking photographs of earth under foggy conditions from great heights?
Question: ‘Heavy water is often used as a moderator in thermal nuclear reactors’. Give reason.

2 Marks Questions:

Question: Explain with the help of diagram the terms:
(i) Magnetic declination and
(ii) Angle of dip at a given place
Question: Two circular coils, one of radius and the other of radius R, are placed coaxially with their centres coinciding. For R>> r, obtain an expression for the mutual inductance of the arrangement.
Question: Find the wavelength of electromagnetic waves of frequency 5 × 1019 Hz in free space. Give its two applications.
Question: Draw the graph showing the variation of binding energy per nucleon with mass number. Give the reason for decrease of binding energy per nucleon for nuclei with high mass numbers.
Question: With the help of a diagram, show the biasing of a light emitting diode (LED). Give its two advantages over conventional incandescent lamps.
Question: A compound microscope with an objective of 1.0 cm focal length and an eye-piece of 2.0 cm focal length has a tube length of 20 cm. Calculate the magnifying power of the microscope, if the final image is formed at the near point of the eye.
Question: The magnifying power of an astronomical telescope in the normal adjustment position is 100. The distance between the objective and the eyepiece is 101 cm. Calculate the focal lengths of the objective and of the eye-piece.
Question: State Gauss’ theorem in electrostatics. Using this theorem, derive the expression for the electric field intensity at any points outside a uniformly charged spherical shell.

3 Marks Questions:

Question: State two conditions to obtain sustained interference of light. In Young’s double slit experiment, using light of wavelength 400 nm, interference fringes of width ‘X’ are obtained. The wavelength of light is increased to 600 nm and the separation between the slits is halved. If one wants the observed fringe width on the screen to be the same in the two cases, find the ratio of the distance between the screen and the plane of the interfering sources in the two arrangements.
Question: Draw the circuit diagram of a common-emitter amplifier using an n-p-n transistor. Draw the input and output wave forms of the signal. Write the expression for its voltage gain.
Question: Write the symbol and truth table of an AND gate. Explain how this gate is realized in practice by using two diodes.
Question: With the help of relevant diagrams, explain the following terms:
(i) Pulse-position modulation (PPM)
(ii) Pulse-duration modulation (PDM)
Question: Name the device used for data transmission from one computer to another. Justify the name. Using this device, draw the block diagram for data communication and explain it briefly.

5 Marks Questions:

Question: 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.
With the help of circuit, show how a moving coil galvanometer can be converted into an ammeter of given range. Write the necessary mathematical formula.
Question: Write an expression for the force experienced by a charged particle moving in a uniform magnetic field B.
With the help of a diagram, explain the principle and working of a cyclotron. Show that cyclotron frequency does not depend on the speed of the particles.
Question: Deduce the condition for balance in a wheat-stone bridge; describe the method to determine the specific resistance of a wire in the laboratory. Draw the circuit diagram and write the formula used. Write any two important precautions you would observe while performing the experiment.

## (CBSE 12th Class Physics 2005 Paper)

1 Mark Questions:

Question: An electric dipole of dipole moment 20 × 10−6 Cm is enclosed by a closed surface. What is the net flux coming out of the surface?

Question: An electron beam, projected along + X-axis, experiences a force due to a magnetic field along the + Y-axis. What is the direction of the magnetic field?

Question: The power factor of an AC circuit is 0.5. What will be the phase difference between voltage and current in this circuit?

Question: Electrons are emitted from a photosensitive surface when it is illuminated by (i) red light (ii) blue light.

Question: What should be the length of the dipole antenna for a carrier wave of frequency 3 × 108 Hz?

Question: Define ‘electric line of force’ and give its two important properties.

Question: State Lenz’s law.

Question: Why is convex mirror used as driver’s mirror?

2 Marks Questions:

Question: Draw V − I graph for ohmic and non-ohmic materials. Give one example for each.

Question: Define the terms ‘Magnetic Dip’ and ‘Magnetic Declination’ with the help of relevant diagrams.

Question: (i) Draw the graphs showing variation of inductive reactance and capacitive reactance with frequency of applied a.c. source.
(ii) Can the voltage drop across the inductor or the capacitor in a series LCR circuit be greater than the applied voltage of the a.c. source? Justify your answer.

Question: The image of a candle is formed by a convex lens on a screen. The lower half of the lens is painted black to make it completely opaque. Draw the ray diagram to show the image formation. How will this image be different from the one obtained when the lens is not painted black?

Question: An electric dipole is held in a uniform electric field. (i) Using suitable diagram, show that it does not undergo any translatory motion, and (ii) derive an expression for the torque acting on it and specify its direction.

Question: Give reasons for the following:
(ii) The small ozone layer on the top of the stratosphere is crucial for human survival.
(iii) Satellites are used for long distance TV transmission.

3 Marks Questions:

Question: Define the term ‘resistivity’ and write its S.I. unit. Derive the expression for the resistivity of a conductor in terms of number density of free electrons and relaxation time.

Question: State the principle of potentiometer. Draw a circuit diagram used to compare the e.m.f. of two primary cells. Write the formula used. How can the sensitivity of a potentiometer be increased?

Question: Explain, with the help of diagram, the principle and working of an a.c. generator. Write the expression for the e.m.f. generated in the coil in terms of its speed of rotation.

Question: A figure divided into squares, each of size 1 mm2, is being viewed at a distance of 9 cm through a magnifying lens of focal length 10 cm, held close to eye.
(a) Draw a ray diagram showing the formation of the image.
(b) What is the magnification produced by the lens? How much is the area of each square in the virtual image?
(c) What is the angular magnification of the lens?

Question: (a) Draw a graph showing the variation of potential energy of a pair of nucleons as a function of their separation. Indicate the regions 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.

Question: Distinguish between analog and digital communication. Write any two modulation techniques employed for the digital data. Describe briefly one of the techniques used.

Question: Draw a schematic diagram of a single optical fibre structure. Explain briefly how an optical fibre is fabricated. Describe in brief, the mechanism of propagation of light signal through an optical fibre.

5 Marks Questions:

Question: (a) With the help of a labelled diagram, explain the principle and working of a moving coil galvanometer.
(b) Two parallel coaxial circular coils of equal radius ‘R’ and equal number of turns ‘N’, carry equal currents ‘I’ in the same direction and are separated by a distance ‘2R’. Find the magnitude and direction of the net magnetic field produced at the mid-point of the line joining their centres.

Question: (a) State Biot-savart’s law. Using this law, derive the expression for the magnetic field due to a current carrying circular loop of radius ‘R’ at a point which is at a distance ‘x’ from its centre along the axis of the loop.
(b) Two small identical circular loops, marked (1) and (2), carrying equal currents, are placed with the geometrical axes perpendicular to each other as shown in the figure. Find the magnitude and direction of the net magnetic field produced at the point O.

Question: (a) How is a wavefront different from a ray? Draw the geometrical shape of the wavefronts when (i) light diverges from a point source, and (ii) light emerges out of the convex lens when a point source is placed at its focus.
(b) State Huygen’s principle. With the help of a suitable diagram, prove Snell’s law of refraction using Huygen’s principle.

Question: (a) In Young’s double slit experiment, deduce the conditions for (i) constructive and (ii) destructive interference at a point on the screen. Draw a graph showing variation of the resultant intensity in the interference pattern against position ‘x’ on the screen.
(b) Compare and contrast the pattern which is seen with two coherently illuminated narrow slits in Young’s experiment with that seen for a coherently illuminated single slit producing diffraction.

Related: MCQ Probability Question Bank

Question: (a) Distinguish between metals, insulators and semiconductors on the basis of their energy bands.
(b) Why are photodiodes used preferably in reverse bias condition? A photodiode is fabricated from a semiconductor with band gap of 2.8 eV. Can it detect wavelength of 6000 nm? Justify.

### (Year 2006)

1 Mark Questions:

Question: Define the term ‘dielectric constant’ of a medium in terms of capacitance of a capacitor.
Question: Sketch a graph showing variation of resistivity of carbon with temperature.
Question: With what purpose was famous Davisson−Germer experiment with electrons performed?
Question: Name the type of communication in which the signal is a discrete and binary coded version of the message or information.
Question: What are the laws of reflection?
Question: Name the physical quantity, whose SI unit is Newton coulomb.
Question: State two factors by which the range of Transmission of signals by a T.V. tower can be increased.

2 Mark Questions:

Question: The electric field and electric potential at any point due to a point charge kept in air is 20 NC−1 and 10 JC−1 respectively. Calculate the magnitude of this charge.
Question: Write the mathematical relation between mobility and drift velocity of charge carriers in a conductor. Name the mobile charge carriers responsible for conduction of electric current in (i) an electrolyte (ii) an ionized gas.
Question: State the principle of working of a cyclotron. Write two uses of this machine.
Question: Draw a labelled ray diagram of a reflecting type telescope. Write its any one advantage over refracting type telescope.
Question: The given graph shows the variation of charge q versus potential difference V for two capacitors C1 and C2. The two capacitors have same plate separation but the plate area of C2 is double than that of C1. Which of the lines in the graph correspond to C1 and C2 and why?
Question: How is the mutual inductance of a pair of coils affected when:
(i) Separation between the coils is increased?
(ii) The number of turns of each coil is increased?(
(iii) A thin iron sheet is placed between the two coils, other factors remaining the same?
Question: A convex lens made up of glass of refractive index 1.5 is dipped, in turn, in:
(i) Medium A of refractive index 1.65
(ii) Medium B of refractive index 1.33
Explain giving reasons, whether it will behave as a converging lens or a diverging lens in each of these two media.
Question: Define the terms threshold frequency and stopping potential in relation to the phenomenon of photoelectric effect. How is the photoelectric current affected on increasing the (i) frequency (ii) intensity of the incident radiations and why?

1 Mark Questions:

Question: Explain with the help of a nuclear reaction in each of the following cases, how the neutron to proton ratio changes during (i) alpha-decay (ii) beta-decay?
Question: What is an intrinsic semiconductor? How can this material be converted into, (i) P-type (ii) N-type extrinsic semiconductor?
Explain with the help of energy band diagrams.
Question: Why is the mass of a nucleus always less than the sum of the masses of its constituents, neutrons and protons?
Question: Draw a graph showing the variation of binding energy per nucleon with mass number for different nuclei. Explain, with the help of this graph, the release of energy by the process of nuclear fusion.
Question: Define the term modulation. Name three different types of modulation used for a message signal using a sinusoidal continuous carrier wave. Explain the meaning of any one of these.
Question: What is electric flux? Write its S.I. units. Using Gauss’s theorem, deduce an expression for the electric field at a point due to a uniformly charged infinite plane sheet.
Question: Define the term ‘critical frequency’ in relation to sky wave propagation of electromagnetic waves.
On a particular day, the maximum frequency reflected from the ionosphere is 10 MHz. On another day, it was found to decrease to 8 MHz. Calculate the ratio of the maximum electron densities of the ionosphere on the two days.
Question: Draw a labelled diagram of Hertz’s experimental set-up to produce electromagnetic waves. Explain the generation of electromagnetic waves using this set-up.

5 Mark Questions:

Question: The primary coil of an ideal step-up transformer has 100 turns and the transformation ratio is also 100. The input voltages and the power are 220 V and 1100 W respectively. Calculate:
(i) Number of turns in the secondary
(ii) The current in the primary
(iii) Voltage across the secondary
(iv) The current in the secondary
(v) Power in the secondary
Question: What is interference of light? Write two essential conditions for sustained interference pattern to be produced on the screen.
Draw a graph showing the variation of intensity versus the position on the screen in Young’s experiment when (a) both the slits are opened and (b) one of the slit is closed.
What is the effect on the interference pattern in Young’s double slit experiment when:
(i) Screen is moved closer to the plane of slits?
(ii) Separation between two slits is increased. Explain your answer in each case.
Question: What is diffraction of light? Draw a graph showing the variation of intensity with angle in a single slit diffraction experiment.
Write one feature which distinguishes the observed pattern from the double slit interference pattern.
How would the diffraction pattern of a single slit be affected when:
(i) The width of the slit is decreased?
(ii) The monochromatic sources of light is replaced by a source of white light?
Question: With the help of a neat and labelled diagram, explain the underlying principle and working of a moving coil galvanometer. What is the function of
(ii) Soft iron core in such a device?
Question: Derive a mathematical expression for the force per unit length experienced by each of the two long current carrying conductors placed parallel to each other in air. Hence define one ampere of current.
Explain why two parallel straight conductors carrying current in the opposite direction kept near each other in air repel?

### (Year 2007)

1 Mark Questions:

Question: An electron, an alpha particle and a proton have the same kinetic energy. Which one of these particles has the largest de-Broglie wavelength?
Question: Why should the material used for making permanent magnets have high coercivity?
Question: Why is frequency modulation preferred over amplitude modulation for transmission of music?

2 Mark Questions:

Question: The output of an OR gate is connected to both the inputs of a NAND gate. Draw the logic circuit of this combination of gates and write its truth table.
Question: Draw a plot of potential energy of a pair of nucleons as a function of their separation. What is the significance of negative potential energy in the graph drawn?
Question: Distinguish between the terms ‘average value ‘and ‘rms value’ of an alternating current. The instantaneous current from an a.c. source is I = 5sin (314t) ampere. What are the average and rms values of the current?
Question: A cylindrical metallic wire is stretched to increase its length by 5%. Calculate the percentage change in its resistance.
Question: Define electric flux. Write its S.I. Units. A spherical rubber balloon carries a charge that is uniformly distributed over its surface. As the balloon is blown up and increases in size, how does the total electric flux coming out of the surface change? Give reason.
Question: Deduce an expression for the electric potential due to an electric dipole at any point on its axis. Mention one contrasting feature of electric of a dipole at a point as compared to that due to single charge.
Question: A parallel plate capacitor, each with plate area A and separation d, is charged to a potential difference V. The battery used to charge it is then disconnected. A dielectric slab of thickness and dielectric constant K is now placed between the plates. What change, if any, will take place in
(i) charge on the plates
(ii) electric field intensity between the plates
(iii) capacitance of the capacitor

3 Marks Questions:

Question: Write the mathematical relation for the resistivity of material in terms of relaxation time, number density and mass and charge of charge carriers in it.
Explain, using this relation, why the resistivity of a metal increases and that of semi-conductor decreases with rise in temperature.
Question: Explain with the help of a labelled diagram the underlying principle and working of a step- up transformer. Why cannot such a device be used to step-up d.c voltage?
Question: Draw a labelled diagram of an a.c generator. Explain briefly its principle and working.
Question: Define the term ‘resolving power’ of an astronomical telescope. How does it get affected on
(i) Increasing the aperture of the objective lens?
(ii) Increasing the wavelength of the light used?
Question: Write any four characteristics of electromagnetic waves. Give two uses each of
Question: In a plot of photoelectric current versus anode potential, how does
(i) the saturation current vary with anode potential for incident radiations of different frequencies but same intensity?
(ii) the stopping potential vary for incident radiations of different intensities but same frequency?
(iii) Photoelectric current vary for different intensities but same frequency of incident radiations?
Question: What is a digital signal? Write two advantages of digital communication. Give any one difference between Fax and E-mail systems of communication.
Question: Explain, with the help of a schematic diagram, the principle and working of a Light Emitting Diode. What criterion is kept in mind while choosing the semiconductor material for such a device? Write any two advantages of Light Emitting Diode over conventional incandescent lamps.

5 Mark Questions:

Question: Draw a labelled diagram of a moving coil galvanometer. State the principle on which it works.
Deduce an expression for the torque acting on a rectangular current carrying loop kept in a uniform magnetic field. Write two factors on which the current sensitivity of a moving coil galvanometer depends.
Question: State Biot-Savart law. Use it to derive an expression for the magnetic field at the centre of a circular loop of radius R carrying a steady current I. Sketch the magnetic field lines for such a current carrying loop.
Question: What are coherent sources? Why are coherent sources required to produce interference of light? Give an example of interference of light in everyday life.
In Young’s double slit experiment, the two slits are 0.03 cm apart and the screen is placed at a distance of 1.5 m away from the slits. The distance between the central bright fringe and fourth bright fringe is 1 cm. Calculate the wavelength of light used.
Question: State the condition under which the phenomenon of diffraction of light takes place. Derive an expression for the width of central maximum due to diffraction of light at a single slit.
A slit of width ‘a’ is illuminated by a monochromatic light of wavelength 700 nm at normal incidence. Calculate the value of ‘a’ for position of
(i) first minimum at an angle of diffraction of 30°
(ii) first maximum at an angle of diffraction of 30°
Question: State the principle of working of p-n diode as a rectifier. Explain, with the help of a circuit diagram, the use of p-n diode as a full wave rectifier. Draw a sketch of the input and output waveforms.
Question: Draw the symbolic representation of a (i) p-n-p, (ii) n-p-n transistor. Why is the base region of transistor thin and lightly doped? With proper circuit diagram, show the biasing of a p-n-p transistor in common base configuration. Explain the movement of charge carriers through different parts of the transistor in such a configuration and show that IE = IC + IB.

### (Year 2008)

1 Mark Questions:

Question: Name the part of the electromagnetic spectrum of wavelength 10−2 m and mention its one application.
Question: An electron and alpha particle have the same de−Broglie wavelength associated with them. How are their kinetic energies related to each other?
Question: A glass 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 make the lens disappear?
Question: State the reason, why heavy water is generally used as a moderator in a nuclear reactor.
Question: How does the fringe width of interference fringes change, upon the whole apparatus of Young’s experiment is kept in a liquid of refractive index 1.3?

2 Marks Questions:

Question: Derive the expression for the electric potential at any point along the axial line of an electric dipole?
Question: Define magnetic susceptibility of a material. Name two elements, one having positive susceptibility and the other having negative susceptibility. What does negative susceptibility signify?
Question: Prove that an ideal capacitor, in an a.c. circuit does not dissipate power.
Question: Derive an expression of the impedance of an ac circuit consisting of an inductor and a resistor.
Question: Draw a ray diagram of a reflecting type telescope. State two advantages of this telescope over a refracting telescope.

3 Marks Questions:

Question: How is a wavefront defined? Using Huygen’s construction draw a figure showing the propagation of a plane wave refracting at a plane surface separating two media. Hence verify Snell’s law of refraction.
Question: Prove that the current density of a metallic conductor is directly proportional to the drift speed of electrons.
Question: A number of identical cells, n, each of emf E, internal resistance r connected in series are charged by a d.c. source of emf E′, using a resistor R.
(i) Draw the circuit arrangement.
(ii) Deduce the expressions for (a) the changing current and (b) the potential difference across the combination of the cells.
Question: Draw a plot of the variation of amplitude versus ω for an amplitude modulated wave. Define modulation index. State its importance for effective amplitude modulation.

5 Marks Questions:

Question: (a) What is plane polarized light? Two Polaroid are placed at 90° to each other and the transmitted intensity is zero. What happens when one more Polaroid is placed between these two, bisecting the angle between them? How will the intensity of transmitted light vary on further rotating the third Polaroid?
(b) If a light beam shows no intensity variation when transmitted through a Polaroid which is rotated, does it mean that the light is un-polarized? Explain briefly.

### (Year 2009)

1 Mark Questions:

Question:What is sky wave propagation?
Question: Write the following radiations in ascending order with respect to their frequencies: X-rays, microwaves, UV rays and radio waves.
Question: Magnetic field lines can be entirely confined within the core of a toroid, but not within a straight solenoid. Why?
Question: If the angle between the pass axis of polarizer and the analyser is 45º, write the ratio of the intensities of original light and the transmitted light after passing through the analyser.

Question: What type of wavefront will emerge from a (i) point source, and (ii) distance light source?
Question: Two nuclei have mass numbers in the ratio 1: 2. What is the ratio of their nuclear densities?

2 Marks Questions:

Question: A cell of emf ‘E’ and internal resistance ‘r’ is connected across a variable resistor ‘R’. Plot a graph showing the variation of terminal potential ‘V’ with resistance R. Predict from the graph the condition under which ‘V’ becomes equal to ‘E’.
Question: (i) Can two equi-potential surfaces intersect each other? Give reasons.
(ii) Two charges −q and +q are located at points A (0, 0, −a) and B (0, 0, +a) respectively. How much work is done in moving a test charge from point P (7, 0, 0) to Q (−3, 0, 0)?
Question: By what percentage will the transmission ranges of TV tower be affected when the height of the tower is increased by 21%?
Question: Derive an expression for drift velocity of free electrons in a conductor in terms of relaxation time.
Question: How does a charge q oscillating at certain frequency produce electromagnetic waves? Sketch a schematic diagram depicting electric and magnetic fields for an electromagnetic wave propagating along the Z-direction.
Question: Why are high frequency carrier waves used for transmission?
Question: What is meant by term ‘modulation’? Draw a block diagram of a simple modulator for obtaining an AM signal.

3 Marks Questions:

Question: A proton and an alpha particle are accelerated through the same potential. Which one of the two has (i) greater value of de Broglie wavelength associated with it, and (ii) less kinetic energy? Justify your answers.
Question: In a single slit diffraction experiment, when tiny circular obstacle is placed in path of light from a distance source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why?
State two points of difference between the interference patterns obtained in Young’s double slit experiment and the diffraction pattern due to a single slit.
Question: (a) Define self inductance. Write its S.I. units.
(b) Derive an expression for self inductance of a long solenoid of length l, cross-sectional area A having N number of turns.
Question: Derive the expression for force per unit length between two long straight parallel current carrying conductors. Hence define one ampere.
Question: Explain the principle and working of a cyclotron with the help of a schematic diagram. Write the expression for cyclotron frequency.

5 Marks Questions:

Question: (a) Derive the relationship between the peak and the rms value of current in an a.c. circuit.
(b) Describe briefly, with the help of labelled diagram, working of a step-up transformer.
A step-up transformer converts a low voltage into high voltage. Does it not violate the principle of conservation of energy? Explain.
Question: (i) Draw a circuit diagram to study the input and output characteristics of an n-p-n transistor in its common emitter configuration. Draw the typical input and output characteristics.
(ii) Explain, with the help of a circuit diagram, the working of n-p-n transistor as a common emitter amplifier.
Question: How is a zener diode fabricated so as to make it a special purpose diode? Draw I-V characteristics of zener diode and explain the significance of breakdown voltage.
Explain briefly, with the help of a circuit diagram, how a p-n junction diode works as a half wave rectifier.
Question: Trace the rays of light showing the formation of an image due to a point object placed on the axis of a spherical surface separating the two media of refractive indices n1 and n2. Establish the relation between the distances of the object, the image and the radius of curvature from the central point of the spherical surface.
Hence derive the expression of the lens maker’s formula.
Question: Draw the labelled ray diagram for the formation of image by a compound microscope.

Derive the expression for the total magnification of a compound microscope. Explain why both the objective and the eyepiece of a compound microscope must have short focal lengths.

### (Year 2010)

1 Mark Questions:

Question: In which orientation, a dipole placed in a uniform electric field is in (i) stable, (ii) unstable equilibrium?
Question: Which part of electromagnetic spectrum is used in radar systems?
Question: Calculate the speed of light in a medium whose critical angle is 30°.
Question: A glass lens of refractive index 1.45 disappears when immersed in a liquid. What is the value of refractive index of the liquid?
Question: Write the expression for Bohr’s radius in hydrogen atom.

2 Mark Questions:

Question: Explain the function of a repeater in a communication system.
Question: (i) Write two characteristics of a material used for making permanent magnets.
(ii) Why is the core of an electromagnet made of ferromagnetic materials? OR
Draw magnetic field line when a (i) diamagnetic, (ii) paramagnetic substance is placed in an external magnetic field. Which magnetic property distinguishes this behaviour of the field line due to the substances?
Question: What is the range of frequencies used in satellite communication? What is common between these waves and light waves?
Question: Find the radius of curvature of the convex surface of a plano-convex lens, whose focal length is 0.3 m and the refractive index of the material of the lens is 1.5.
Question: An electron is accelerated through a potential difference of 64 volts. What is the de-Broglie wavelength associated with it? To which part of the electromagnetic spectrum does this value of wavelength correspond?
Question: (i) Out of blue and red light which is deviated more by a prism? Give reason.
(ii) Give the formula that can be used to determine refractive index of materials of a prism in minimum deviation condition.
Question: Plot a graph showing the variation of stopping potential with the frequency of incident radiation for two different photosensitive materials having work functions W1 and W2 (W1 > W2). On what factors does the (i) slope and (ii) intercept of the lines depend?
Question: Draw the circuit diagram of an illuminated photodiode in reverse bias. How is photodiode used to measure light intensity?
Question: A heavy nucleus X of mass number 240 and binding energy per nucleon 7.6 MeV is split into two fragments Y and Z of mass numbers 110 and 130. The binding energy of nucleons in Y and Z is 8.5 MeV per nucleon. Calculate the energy Q released per fission in MeV.

3 Mark Questions:

Question: What is space wave propagation? Give two examples of communication system which use space wave mode. A TV tower is 80 m tall. Calculate the maximum distance upto which the signal transmitted from the tower can be received.
Question: What is an unpolarized light? Explain with the help of suitable ray diagram how an unpolarized light can be polarized by reflection from a transparent medium. Write the expression for Brewster angle in terms of the refractive index of denser medium.
Question: Write the principle of working of a potentiometer. Describe briefly, with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a given cell.
Question: A long straight wire of a circular cross-section of radius ‘a’ carries a steady current ‘I’. The current is uniformly distributed across the cross-section. Apply Ampere’s circuital law to calculate the magnetic field at a point ‘r’ in the region for (i) r < a and (ii) r > a. OR
State the underlying principle of working of a moving coil galvanometer. Write two reasons why a galvanometer can not be used as such to measure current in a given circuit. Name any two factors on which the current sensitivity of a galvanometer depends.
Question: A parallel-plate capacitor is charged to a potential difference V by a dc source. The capacitor is then disconnected from the source. If the distance between the plates is doubled, state with reason how the following change:
(i) electric field between the plates
(ii) capacitance, and
(iii) energy stored in the capacitor

5 Mark Questions:

Question: Describe briefly, with the help of a labelled diagram, the basic elements of an A.C. generator. State its underlying principle. Show diagrammatically how an alternating emf is generated by a loop of wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf induced in the rotating loop.
Question: State Huygens’s principle. Show, with the help of a suitable diagram, how this principle is used to obtain the diffraction pattern by a single slit.
Draw a plot of intensity distribution and explain clearly why the secondary maxima becomes weaker with increasing order (n) of the secondary maxima.
Question: Draw a ray diagram to show the working of a compound microscope. Deduce an expression for the total magnification when the final image is formed at the near point.
Question: In a compound microscope, an object is placed at a distance of 1.5 cm from the objective of focal length 1.25 cm. If the eye piece has a focal length of 5 cm and the final image is formed at the near point, estimate the magnifying power of the microscope. 