Students must start practicing the questions from RBSE 12th Physics Model Papers E- Physics Self Evaluation Test Papers in English Medium provided here.

## RBSE Class 12 E-Physics Self Evaluation Test Papers in English

General Instructions to the Examinees :

- Candidate must write first his/her Roll Nc. on the question paper compulsorily.
- All the questions are compulsory.
- Write the answer to each question in the given answer book only.
- For questiotis having more than one part the answers to those parts arc to be written together in continufty.

**RBSE Class 12 E- Physics Self Evaluation Test Paper 1 in English**

Section- A

1. Write the eorrct answer from multiple choice question 1 (i to ix) and write th in given answer book

(i) Total electric flux coming out of a unit positive change pui in air is: [1]

(a) ε_{0}

(b) ε^{-1}

(c) \(\frac{q}{4 \pi \varepsilon_{0} a}\)

(d) 4πε_{0}

(ii) Two conducting sphctcs of raddi r_{1} and r_{2} are equally charged. The ratio of their potential is: [1]

(a) \(\frac{r_{1}}{r_{2}}\)

(b) \(\frac{r_{2}^{2}}{r_{1}^{2}}\)

(c) \(\frac{r_{2}}{r_{1}}\)

(d) \(\frac{r_{1}^{2}}{r_{2}^{2}}\)

(iïi) Reciprocal of resucance is known as

(a) Specific cooductivity

(b) Conductivity

(c) Resistivity

(d) None of these

(iv) The cyclotron frequency v_{c} is given by [1]

(a) \(\frac{q \mathrm{~B}}{2 \pi m}\)

(b) \(\frac{m \mathrm{~B}}{2 \pi q}\)

(c) \(\frac{2 \pi m}{q \mathrm{~B}}\)

(d) \(\frac{2 \pi}{q B}\).

(v) Two similar circular co-axial loops carry equal currents in the same direction.

If the loops be brought nearer, the current in loops [1]

(a) Decreases

(b) Increases

(c) Remains same

(d) Different in each loop

(vi) Which one among the following shows particle nature of tight? [1]

(a) Photoelectric effect

(b) Interference

(c) Refraction

(d) Polarization

(vii) A radioactive susbtance has a half life of 1 year. The fraction of this material, that would remain after 5 years will

be [1]

(a) \(\frac{1}{32}\)

(b) \(\frac{1}{5} \)

(c) \(\frac{1}{2}\)

(d) \(\frac{4}{5} \)

(viii) The resistance of semiconductor and conductor- [1]

(a) Increase with temperature for both of them

(b) Decrease with temperature for both of them

(c) Increase and decreases with temperature

(d) None of these

(ix) The given symbol represents – [1]

(a) OR gate

(b) NOR gaie

(c) NOT gate

(d) AND gate

Question 2.

Fill in the blanks :

(i) Potential inside a shell is …………………………… . [1]

(ii) Kirchhoff’s second law supports the law of conservation of ………………………………. .[1]

(iii) Maieutic flux is a scalar quantity and its dimensional formula is ……………………… .[1]

(iv) gives an inverted version of its input ………………………… .[1]

Question 3.

Give the answer of the following question in one line.

(i) State the underlying principle of potentiometer. [1]

(ii) Draw the magnetic field lines due to a current-carrying loop. [1]

(iii) Two spherical bobs, one metallic and other of glass, of the same size are allowed to fall freely from the same height above the ground. Which of the two would reach earlier and why? [1]

(iv) Why is photoelectric emission not possible at all frequencies? [1]

(v) Show graphically. the variation of de-Broglie wavelength (λ) with the potential (v) through which an electron is accelerated from rest. [1]

(vi) Two nuclei have mass numbers in the ratio 27: 125. What is the ratio of their nuclear radii? [1]

(vii) Why is the detection of neutrinos found very difficult? [1]

(viii) Give the logic symbol of NOR gate. [1]

Section-B

Question 4.

Derive the expression for the electric potential due to an electric dipole at a point on its axial line. [1½]

Question 5.

Calculate the potential differences and the energy stored in the capacitor C_{2} in the circuit shown in the figure. Given potential at A is 90V, C_{1} = 20µF, C_{2} = 30µF and C_{3} = 15µF. [1½]

Question 6.

Using the concept of drift velocity of charge carriers in a conductor, deduce the relationship between current density and resistivity of the conductor. [1½]

Question 7.

Use Kirchhoff’s rules to obtain balance conditions in a Wheatstone bridge. [1½]

Question 8.

A long solenoid with 15 turns per cm has a small loop of area 2.0 cm^{2} placed inside the solenoid normal to its axis.

If the current carries by the solenoid change steadily from 2.0 to 4.0 in 0.1s. Then what is the induced emf in the loop while the current in changing?[1½]

Question 9.

Define natural induction. Write SI unit and dimensional formula.[1½]

Question 10.

Use the mirror equation to show then on object placed between F and 2F of a concave mirror produces a real image

beyond 2F. [1½]

Question 11.

Draw a schematic arrangement of a reflecting telescope showing how rays coming from a distant object are received at the eyepiece. Write its two important advantages over a refracting telescope. [1½]

Question 12.

An object of 3 cm height is placed at a distance of 60 cm from a convex mirror of focal length 30 cm. Find the nature,

position and size of the image fonned. [1½]

Question 13.

Write the conditions for observing a rainbow. Show by drawing suitable diagram how one understands the formation of rainbow. [1½]

Question 14.

expression N = N_{0}e for the law of radioactive decay. [1½]

Question 15.

Calculate the energy release in MeV in the deuterium-tritium fusion reaction. [1½]

_{12}H + _{13}H → _{24}He+_{e1}n

Using the data m(_{12}H) =2.014102 u; m(_{13}) =3.016049 u; m(_{24}He) =4.002603 u;m_{n} = 1.0086654; 1u= 931.5\(\frac{\mathrm{MeV}}{\mathrm{C}^{2}}\)

Section-C

Question 16.

Write using Biot-Savart law, the expression for the magnetic field B due to an element dl carrying current I at a distance r from it in a vector form. Hence drive the expression for the magnetic field due to a current-carrying loop of radius R at center O. [3]

OR,

Using Ampere’s circuital law, obtain the expression for the mangetic field due to a long solenoid at a point inside the solenoid on its axis. [3]

Question 17.

Draw a labelled ray diagram to show the formation of image in an astronomical telescope for a distant object.

Derive the expression for its magnifying power in normal adjustment. [3]

OR

Draw a neat labelled ray diagram of a compound microscope. Explain briefly its working. [3]

Question 18.

(i) Define the terms threshold frequency and stopping potential in the study cf photoelectric emission. [3]

(ii) Explain briefly the reasons why wave theory of light is not able to explain the observed features in photoelectric effect?

OR

Write Einstein photoelectric equation. State clearly how this equation is obtained using the photon picture of electromagnetic radiation.

Write the three salient features observed in photoelectric effect which can be explained using the equation. [3]

Section-D

Question 19.

State Gauss’s law in electrostatics. Using this law, derive an expression for the electric field due to a uniformly charged infinite plane sheet. [4]

OR

Define the term electric dipole moment. It is a scalar or vector? Deduce an expression for the electric field at a point on the equatorial plane of an electric dipole of length 2a. [4]

Question 20.

Draw the typical shape of the V-I characteristics of a p-n junction diode both in (a) forward (b) reverse bias configuration. How do we infer, from these characteristics that a diode can be used to rectify alternating voltages. [4]

OR

State the main practical application of LED. Explain giving reason, why the semiconductor used for fabrication of visible light LED’s must have a bandgap of at least 1.8 eV. [4]

**RBSE Class 12 E-Economics Self Evaluation Test Paper 2 in English**

Section-A

Question 1.

Write the correct answer from multiple choice question 1 (i to ix) and write the in given answer book.

(i) If \(\oint \overrightarrow{\mathrm{E}} \cdot d \overrightarrow{\mathrm{S}}\) = 0 over a surface, Then : [1]

(a) The electric field inside the surface and on it is zero

(b) The electric field inside the surface in necessarily uniform

(c) All changes most necessarily be outside the surface

(d) All of these.

(ii) Figure shows the field lines of a positive point charge. The work done by the field in moving a small positive charge from Q to P is :

[1]

(a) Zero

(b) Positive

(c) Negative

(d) Data insufficient

(iii) Relation between drift velocity and current [1]

(a) v_{d} = \(\frac{n e \mathrm{~A}}{\mathrm{I}}\)

(b) v_{d} = \(\frac{\mathrm{I}}{n e \mathrm{~A}}\)

(c) v_{d} = IneA

(d) v_{d} = \(\frac{n \mathrm{I}}{e \mathrm{~A}}\)

(iv) The magnetic force \(\overrightarrow{\mathrm{F}}\) on a current carrying conductor of length l in on external magnetic field \(\overrightarrow{\mathrm{B}}\) is given by : [1]

(a) \(\frac{I \times \vec{B}}{\vec{l}}\)

(b) \(\frac{\vec{i} \times \overrightarrow{\mathrm{B}}}{\mathrm{I}}\)

(c) I \((\vec{l} \times \overrightarrow{\mathrm{B}})\)

(d) I^{2} \((\vec{l} \times \overrightarrow{\mathrm{B}})\)

(v) Direction of current induced in wire moving in a magnetic field is found using : [1]

(a) Fleming’s left-hand rule

(b) Fleming’s right-hand rule

(c) Ampere’s rule

(d) Right-hand dasp rule

(vi) In photoelectric effect the photocurrent: [1]

(a) Depends both on intensity and frequency of the incident light.

(b) Does not depend on the frequency of incident light but depends on the intensity of the incident light.

(c) Decreases with increase in frequency of incident light.

(d) Increases with increase in frequency of incident light.

(vii) Which is the correct expression for half life- [1]

(a) t_{1/2} = log 2

(b) (t)_{1/2} = \(\frac{\lambda}{\log 2}\)

(c) t_{1/12} = \(\frac{\lambda}{\log 2} 2.303\)

(d) t_{1/12} = I^{2} \((\vec{l} \times \overrightarrow{\mathrm{B}})\).

(viii) To get an output Y = 1 is given circuit which of the following input will be correct- [1]

(ix) C and Si both have same lattice structure having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because : [1]

(a) incase of C, the valence band is not completely filled at absolute zero temperature.

(b) In case of C the conduction band is partly filled even at absolute zero temperature.

(c) The four bonding electrons in the case of 0 lie in the second orbit; whereas in the case of Si they lie in the third.

(d) The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the second.

Question 2.

Fill in the blanks :

(i) Work done in moving at test charge from one point to equipotential surface to other is …………………… . [1]

(ii) The terminal voltage increases with the increase of ………………………… .[1]

(iii) For the motion’ parallel to \(\overrightarrow{\mathrm{B}}\), the induced emf is ………………………. .[1]

(iv) Boolean expression of AND gate is given as …………………………. . [1]

Question 3.

Give the answer of the following question in one line.

(i) The emf of a cell is always greater than its. terminal voltage. Why? Give reason. [1]

(ii) Use the expression F = q\((\vec{v} \times \overrightarrow{\mathrm{B}})\) to define the SI unit of magnetic field. [1]

(iii) Predict the direction of induced current in metal rings 1 and 2 when current I in the wire is steadily decreasing. [1]

(iv) Show the variation on photoelectric current with collector plate potential for different frequencies but same intensity of incident radiation. [1]

(v) Write the expression of de-Broglie wavelength associated with a charged particle having charge q and mass m.

When it is accelerated by a potential. [1]

(vi) A nucleus undergoes β-decay. How does its (a) mass number and (b) atomic number change? [1]

(vii) Draw the plot of bindings energy per nucleon BE/A as a function of mass number A. [1]

(viii) A given logic gate inverts the input applied to it. Name this gate and give its symbol. [1]

Section-B

Question 4.

Define an equipotential surface. Draw equipotential surfaces- (i) in case of a single point charge, (ii) in a constant electric field in z-direction. [1½]

Question 5.

Net capacitance of three identical capacitors in series is 1 µF. What will be their net capacitance, if connected in parallel? Find the ratio of energy stored in these two configurations if they are both connected to the same sources. [1½]

Question 6.

Derive an expression for the current density of a conductor in terms of the drift speed of electrons. [1½]

Question 7.

Describe briefly with the help of a circuit diagram, how a potentiometer is used to determine the internal resistance of a cell. [1½]

Question 8.

Derive an expression for the mutual inductance of two long coaxial solenoids of same length wound one over the other. [1½]

Question 9.

Draw a labelled diagram of AC generator and state its working principle. [1½]

Question 10.

Explain briefly how the phenomenon of total internal reflection is used in fibre optics. [1½]

Question 11.

Draw a diagram showing the formation of primary rainbow and explain at what angles the primary raindow is visible. [1½]

Question 12.

Two thin lenses of power- 4D and 2D are placed in contact coaxially. Find the focal length of the combination. [1½]

Question 13.

The image obtained with a convex lens is erect and its length is four times the length of the object.[1½]

Question 14.

Show that the density of nucleus over a wide range of nuclei is constant and independent of mass number A.[1½]

Question 15.

A radioactive nucleus A undergoes a series of decays according to the following scheme

mass number and atomic number of A4 are 172 and 69, respectively. What are these numbers for A?[1½]

Section-C

Question 16.

Draw a schematic sketch of a cyclotron. Explain clearly the role of crossed electric and magnetic field in accelerating the charge. Hence, derive the expression for the kinetic energy required by the particles. [3]

OR

Draw a labelled diagram of a moving coil galvanometer. Describe briefly its principle and working. [3]

Question 17.

Draw a ray diagram showing the formation of the image by a point object on the principal axis of a spherical convex surface separating two media of refractive indices n_{1} and n_{2}, when a point source is kept in rarer medium of refractive index n_{1}. Derive the relation between object and image distance in terms of refractive index of the medium and radius of curvature of the surface.[3]

OR

When a ray of light passes through a triangular glass prism, find out the relation for the total deviation. δ in terms of the angle of incidence i and angle of emergence, e [3]

Question 18.

(i) Define the term stopping potential. [3]

(ii) Plot a graph showing the variation of photoelectric current as a function of anode potential for two light beams having the same frequency but different intensities I_{1} and I_{2} (I_{1} > I_{2})

(iii) The stopping potential in an experiment on photoelectric effect is 2V. What is the maximum kinetic energy of the photoelectrons emitted?

OR

An electron and a proton 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 momentum? Justify your answer. [3]

Section-D

Question 19.

State Gauss’s lay Use it to deduce the expression for the electric field due to a uniformly charged thin spherical shell at points (a) inside the shell and (b) outside the shell. [4]

OR

A charge in distributed uniformly over a ring of radius a. Obtain an expression for the electric field intensity E at a point on the axis of the ring. Hence show that for points at large distances from the ring, it behaves like a point charge. [4]

Question 20.

(i) Why are NAND gate called universal gates? Identify the logical operations carried out by the circuit given as below.

(ii) Draw the logic circuit of AND gate and write its truth table. [4]

OR

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. [4]

**RBSE Class 12 E-Physics Self Evaluation Test Paper 3 in English**

Section-A

Question 1.

Write the correct answer from multiple choice question 1 (i to ix) and write the in given answer book

(i) The S.l unit of electric flux is: [1]

(a) N/C^{1}m^{2}

(b) N/C m^{2}

(c) N/C^{2} m^{2}

(d) N/C^{2} m^{2}

(ii) In a region of constant potential : [1]

(a) The electric field is uniform

(b) There electric field is zero

(c) There can be no charge inside the region

(d) Both (b) and (c) are correct

(iii) Resistance of a resistor is inversely proportional to: [1]

(a) area of cross-section

(b) length

(c) both (a) and (b)

(d) None of these

(iv) A strong magnetic field is applied on stationary electrons. Then the electron : [1]

(a) Moves in the direction of the field

(b) Remains stationary

(c) Moves perpendicular to the direction of the field

(d) Moves opposite to the direction of the field

(v) Lenz’s law is a consequence of the law of conservation of: [1]

(a) Charge

(b) Energy

(c) Induced emf

(d) Induced current

(vi) In photoelectric effect, the photoelectric current is independent of: [1]

(a) Intensity of incident light

(b) Potential difference applied between the two electrodes

(c) The nature of emitter material

(d) Frequency of incident light

(vii) After two hours one-sixteenth of the initial amount of a certain radioactive isotope remained undecayed. The half-life of the isotope is : [1]

(a) 15 minutes

(b) 30 minutes

(c) 45 minutes

(d) One hours

(viii) The following logic circuit represents : [1]

(a) NAND gate with output O = \(\bar{X}+\bar{Y}\)

(b) NOR gate with output O = \(\overline{X+Y}\)

(c) NAND gate with output O = \(\overline{\mathrm{XY}}\)

(d) NOR gate with output O = \(\bar{X}+\bar{Y}\)

(ix) A piece of copper and the other of Germanium are cooled from the room temperature to 80 K, then which of the following would be a correct statement: [1]

(a) Resistance of each increases

(b) Resistance of each decreases

(c) Resistance of Copper increases while that of Germanium decreases

(d) Resistance of Copper descreases while that of Germanium increases.

Question 2.

Fill in the blanks :

(i) Capacitance of an isolated spherical conductor of radius r is given by ………………………… . [1]

(ii) The emf of two primary cells can be compared using potentiometer as ………………………… . [1]

(iii) SI unit of magnetic flux is ………………………… . [1]

(iv) …………………………. converts solar energy into electrical energy . [1]

Question 3.

Given the answer of the following question in one line.

(i) The three coloured bands, on a carbon resistor are red, green and yellow respectively. Write the value of its

resistance. [1]

(ii) A beam of a-particles projected along + X-axis, experiences a force due to a-magnetic field along the +Y axis. What is the direction of the magnetic force. [1]

(iii) On what factors does the magnitude of the emf induced in the circuit due to magnetic flux depend ? [1]

(iv) Show on a plot the nature of variation of photoelectric current with the intensity of radiation incident on a photosensitive surface. [1]

(v) A proton and electron have same kinetic energies. Which one has greater than de-Broglie wavelength and why? [1]

(vi) How is the radius of a nucleus related to its mass numbers? [1]

(vii) Write any two characteristic properties of nuclear force. [1]

(viii) What is the difference between an n-type and a p-type extrinsic semiconductor? [1]

Section-B

Question 4.

Two-point charges q_{1} and q_{2} are located at r_{1} and r_{2}, respectively in an external electric field E. Obtain the expression for the total work done in assembling this configuration. [1½]

Question 5.

Deduce the expression for the electrostatic energy stored in a capacitor of capacitance C and having charge Q. [1½]

Question 6.

Define mobility of charge carrier. Write the relation expressing mobility in terms of relaxation time.[1½]

Question 7.

A potentiometer wire of length lm has a resistance of 5 Ω. It is connected to a 8V battery in series with a resistance of

15Ω. Determine the emf of the primary cell which gives a balance point at 60 cm. [1½]

Question 8.

A pair of adjacent coils has a mutual inductance of 1.5 H. If the current in one coil changes from 0 to 20 A in 0.5 s. What is the change of flux linkage with the other coil?[1½]

Question 9.

Due to the presence of the current in rod and of the magnetic field, Find the expression for the. magnitude and direction of the force acting on this rod. [1½]

Question 10.

A convex lens of focal length F_{1} is kept in contact with a concave lens of Focal length F_{2}. Find the focal length of the combination.[1½]

Question 11.

Write the necessary condition for the phenomenon of total internal reflection to occur. Write the relation between the refractive index and critical angle for a given pair of optical media.[1½]

Question 12.

Draw a ray diagram to show the image formation by a concave mirror. When the object is kept between its focus and the pole. Using this diagram, derive the magnification formula for the image formed. [1½]

Question 13.

A convex lens has 10cm focal length in air. What is its focal length in water? (Refractive index of air-water = 1.33 and

refractive index of air-glass = 1.5) [1½]

Question 14.

Derive an expression for that average life of a radionuclide. Give its relationship with the half-life.[1½]

Question 15.

Write three characteristic properties of nuclear force.[1½]

Section-C

Question 16.

Explain using a labelled diagram, the principle and working of a moving coil galvanometer. What is the function of

(i) uniform radial magnetic field

(ii) soft iron core? [3]

OR

Two straight long parallel conductors carry currents I_{1} and I_{2} is the same direction. Deduces the expression for the force per unit length between them. Depict the pattern of magnetic field lines and them. [3]

Question 17.

Draw a ray diagram to show refraction of a ray of monoch somatic light passing through a glass prism. Deduce the

expression for the refractive index of glass in terms of angle of prism and angle of minimum deviation. [3]

OR

With the help of a suitable ray diagram derive a relation between object distance (u), image distance (v) and radius of curvature (R) for the convex spherical surface when a ray of light travels from a rarer to denser medium. [3]

Question 18.

(i) State de-Broglie hypothesis.

(ii) Derive an expression for the de-Broglie wavelength associated with an electron accelerated through a potential V.

(iii) Draw a schematic diagram of a localized wave describing the wave nature of the moving electron. [3]

OR

Define the term “Cut-off frequency” in photoelectric emission. The threshold frequency of a metal is f. when the light of frequency 2F is incident on the metal plate, the maximum velocity of photoelectron is v_{1}. When the frequency of the incident radiation is increased to 5f, the maximum velocity of photo electron is v_{2}. Find the ratio v_{1} = v_{2}. [3]

Section-D

Question 19.

(i) Define torque acting on a dipole of dipole moment \(\vec{P}\) placed in a uniform electric field \(\overrightarrow{\mathrm{E}}\) .

Express it in the vector form and point out the direction along which it acts.

(ii) What happens if the field is non-uniform?

(iii) What would happens if the external field \(\overrightarrow{\mathrm{E}}\) is increasing (a) parallel to \(\overrightarrow{\mathrm{P}}\) and (b) anti-parallel to \(\overrightarrow{\mathrm{P}}\) ? [4]

OR

State Gauss’s law in electrostatics. Using this law derive an expression for the electric field due to a long straight wire of linear charge density k c/m. [4]

Question 20.

(i) Explain with the help of diagram, how a depletion layer and barrier potential are formed in a junction diode.

(ii) Draw a circuit diagram of a full-wave rectifier. [4]

OR

Name the device which is used as a voltage regulator. Draw the necessary circuit diagram and explain its working. [4]

**RBSE Class 12 E-Physics Self Evaluation Test Paper 4 in English**

Section-A

Question 1.

Write the correct answer from multiple choice question I (I to ix) and write the in given answer book.

(i) According to Gass’s Theorem, electric field of an infinitely long straight wire is proportional to: [1]

(a) r

(b) \(\frac{1}{r^{2}} \)

(c) \(\frac{1}{r^{3}}\)

(d) \(\frac{1}{r}\)

(ii) Which of the following statement s not true? [1]

(a) Electrostatic force is a conservative force

(b) Potential at a point is the work dine per unit charge in bringing a charge from infinity to that point.

(c) Ap equipotential surface is a surface over which potential has a constant value.

(d) Inside a conductor, electrostatic field is zero.

(iii) Equivalent resistance of the given network is : [1]

(a) 28

(b) 18

(c) 26

(d) 25

(iv) A charged particle would continue to move with a constant velocity in a region wherein, which of the following

conditions is not correct? [1]

(a)E=0, B ≠ 0

(b) E ≠ 0, B≠ 0

(c) E ≠ 0,B=0

(d) E=0,B=0

(v) The magnetic flux linked with a coil of N turns of area of cross-section A held with its plane parallel to the field B

is: [1]

(a) \(\frac{\mathrm{NAB}}{2}\)

(b) NAB

(c) \(\frac{\text { NAB }}{4}\)

(d) Zero

(vi) Light of wavelengths falls on a metal having work functions λC/λ_{0}. Photoelectric effect will take place only. 1[]

(a) λ ≥ λ_{0}

(b) λ ≤ λ_{0}

(c) λ ≥ 2λ_{0}

(d) λ = 4λ_{0}

(vii) Equivalent energy of mass equal to 1 amu is: [1]

(a) 93 KeV

(b) 931 eV

(c) 931 MeV

(d) 9.31 MeV

(viii) The figure shows a logic circuit with two inputs A and B and the output C. The voltage wavefront across A, B, and C are as given. The logic circuit gate is: [1]

(a) OR gate

(b) NOR gate B

(c) AND gate

(d) NAND gate

(ix) Which one of the following represents forward bias diode? [1]

Question 2.

Fill in the blanks :

(i) A capacitor is a device which is used to store …………………………………….. energy .[1]

(ii) The sensitivity of potentiometer can be ……………………………. by increasing the number of wires of potentiometer. [1]

(iii) An AC generator is based on the phenomenon of ……………………………. .[1]

(iv) Zener diode, is a ……………………… biased heavily doped p-n junction diocle. [1]

Question 3.

Give the answer of the following question in one line:

(i) I-V graph for metallic wires at two different temperatures T_{1} and T_{2} is as shown in the figure below. Which of the two temperatures is lower and why? [1]

(ii) Write the expression in a vector form for the Lorentz magnetic forme F due to a charge moving with velocity \(\vec{v}\)

in a magnetic field \(\overrightarrow{\mathrm{B}}\) . [1]

(iii) In the given figure, a bar magnet is quickly moved towards a conducting loop having a capacitor.

Predict the polarity of the plates A and B of the capacitor. [1]

(iv) Define intensity of radiation on the basis of photon picture of light. Write its SI unit. [1]

(v) Draw a plot showing the variation of de-Broglie wavelength of the electron as a function of it K.E. [1]

(vi) A nucleus _{92238}U undergoes a-decay and transform to Thorium, What is

(a) the mass number and

(b) atomic number of the nucleus produced ? [1]

Calculate the energy in fusion reaction.

_{12}H+_{12}H →_{23}He + _{01}n + energy,

where BE of _{12}H = 2.23 MeV and of _{23}He = 7.73 MeV.

(viii) What is the most common use of photodiode ? [1]

Section-B

Question 4.

Find out the expression for the potential energy of a system of three charges q_{1}, q_{2} and q_{3} located at r_{1},r_{2}

and r_{3} with respect to the common origin O. [1½]

Question 5.

Find the charge on the capacitor as shown in the figure. [1½]

Question 6.

Derive an expression for drift velocity of free electrons in a conductor in terms of relaxation time. [1½]

Question 7.

In a meter bridge, the null point is found at a distance of 40 cm from A. If a resistance of 12Ω is connected in parallel with S. Then null point occurs at 50 cm from A. Determine the value of R and S.[1½]

Question 8.

State Faraday’s law of electromagnetic induction. [1½]

Question 9.

A jet plane is travelling towards west at a speed of 1800 km/h. What is the voltage difference developed between the ends of the wing having a span of 25m, if the earth’s magnetic field at the location has magnitude of 5 x 10^{-4} T and the dip angle is 30°? [1½]

Question 10.

Flow does focal length of a lens change when red light incident on it is replaced by violet light Give, reason for your

answer. [1½]

Question 11.

(i) Why does the sun appear reddish at Sunset or Sunrise?

fii) For which colour, the refractive index of pism material is maximum and minimum? [1½]

Question 12.

Write the three distinct advantages of a reflecting type telescope over a refracting type telescope. [1½]

Question 13.

The near point of a hypermetropic person is 50 cm from the eye. What is the power of the lens required to enable the person to read clearly a book held at 25 cm from the eye? [1½]

Question 14.

A radioactive nucleus has a decay constant λ = 0.3465 (day)^{-1}, How long would it take the nucleus of decay to 75% of

its initial amount? [1½]

Question 15.

Define the Q-value of a nuclear process, when can a nuclear process not proceed spontaneously? [1½]

Section-C

Question 16.

Write the expression for the force \(\overrightarrow{\mathrm{F}}\) acting on a particle of mass m and charge q moving with velocity \(\vec{v}\) in a magnetic field \(\overrightarrow{\mathrm{B}}\) Under what conditions will it move in (a) a circular path and (b) a helical path? [3]

Or

Obtain an expression for the force experienced by a current-carrying wire in a magnetic field. [3]

Question 17.

Use the mirror equation to show that:

(a) An object placed between / and 2f of a concave mirror produces a real image beyond If,

(b) A convex mirror always produces a virtual image independent of the location of the object.

(c) An object placed between the pole and the focus of a concave mirror produces a virtual and enlarged image. [3]

OR

Plot a graph to show variation of the angle of deviation as a function of angle of incidence for light passing through a prism. Derive an expression for refractive index of the prism interms of angle of minimum deviation and angle of prism. [3]

Question 18.

A beam of monochromatic radiation is incident on a photosensitive surface. Answer the following questions giving reasons.

(a) Do the emitted photoelectron have the same kinetic energy?

(b) Does the kinetic energy of the emitted electrons depend on the intensity of incident radiation?

(c) On what factors does the number of emitted photoelectrons depend? [3]

OR

Write Einstein’s photoelectric equation and point out any two characteristic properties of photons on which this equation is based. Briefly explain three observed features which can be explained by this.equation. [3]

Section-D

Question 19.

State Gauss’s law. A thin straight infinitely long conducting wire of linear charge density X is enclosed by a cylindrical

surface of radius r and length l. Its axis coinciding the expression for the electric field, indicating its direction at a point on the surface of the cylinder. [4]

OR

(i) Define electric flux.

(ii) Using Gauss’s law, prove that the electric field at a point due to a uniformly charged infinite plane sheet is independent of distance from it. How is the field directed if (a) the sheet is positively charged ? (b) negatively charged. [4]

Question 20.

(i) How is a depletion region formed in p -n junction?

(ii) With the help of a labelled circuit diagram. Explain how a junction diode is used as a full-wave rectifier.

Draw its input, output wavefront. [4]

OR

Give logic symbol, boolean expression and truth table for logic gate: OR gate, AND gate, NOT gate and NAND gate. [4]

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