Physics Sample Paper Class 12 with Marking Scheme.

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Sample Paper

Class 12

Physics

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                                 Class: XII 

                        Session: 2020-2021

                          Subject: Physics

              Sample Question Paper (Theory)

Maximum Marks: 70                                                         Time Allowed: 3 hour

General Instructions:

(1) All questions are compulsory. There are 33 questions in all. 

(2) This question paper has five sections: Section A, Section B, Section C, Section D and

Section E.

(3) Section A contains ten very short answer questions and four assertion reasoning

MCQs of 1 mark each, Section B has two case based questions of 4 marks each, 

Section C contains nine short answer questions of 2 marks each, Section D contains 

five short answer questions of 3 marks each and Section E contains three long answer 

questions of 5 marks each.

(4) There is no overall choice. However internal choice is provided. You have to attempt 

only one of the choices in such questions.

                                               Section – A

All questions are compulsory. In case of internal choices, attempt 

any one of them. 

1. Name the physical quantity having unit J/T. 

2 Mention one use of part of electromagnetic spectrum to which a wavelength 

of 21 cm (emitted by hydrogen in interstellar space) belongs.

OR

Give the ratio of velocity of the two light waves of wavelengths 4000Å and 

8000Å travelling in vacuum.

3  An electron with charge -e and mass m travels at a speed v in a plane 

perpendicular to a magnetic field of magnitude B. The electron follows a 

circular path of radius R. In a time, t, the electron travels halfway around the 

circle. What is the amount of work done by the magnetic field?

4 A solenoid with N loops of wire tightly wrapped around an iron-core is 

carrying an electric current I. If the current through this solenoid is reduced 

to half, then what change would you expect in inductance L of the solenoid.

 OR

An alternating current from a source is given by i=10sin314t. What is the 

effective value of current and frequency of source?

5  What is the value of angular momentum of electron in the second orbit of 

Bohr’s model of hydrogen atom? 

6  In a photoelectric experiment, the potential required to stop the ejection of electrons from cathode is 4V. What is the value of maximum kinetic energy of emitted Photoelectrons?

7  In decay of free neutron, name the elementary particle emitted along with 

proton and electron in nuclear reaction.

OR

In the following nuclear reaction, Identify unknown labelled X.

8   How does the width of a depletion region of a pn junction vary if doping 

concentration is increased?

OR

In half wave rectification, what is the output frequency if input frequency is 

25 Hz.

9  When a voltage drop across a pn junction diode is increased from 0.70 V to 

0.71V, the change in the diode current is 10 mA .What is the dynamic 

resistance of diode?

10  Which specially fabricated pn junction diode is used for detecting light 

intensity?

For question numbers 11, 12, 13 and 14, two statements are given-one 

labelled Assertion (A) and the other labelled Reason (R). Select the 

correct answer to these questions from the codes (a), (b), (c) and (d) 

as given below.

a) Both A and R are true and R is the correct explanation of A 

b) Both A and R are true but R is NOT the correct explanation of A 

c) A is true but R is false

d) A is false and R is also false

11.   Assertion(A) : In a nonuniform electric field, a dipole will have translatory as well as rotatory motion.

Reason(R): In a nonuniform electric field, a dipole experiences a force as well as torque.

12 Assertion(A): Electric field is always normal to equipotential surfaces and along the direction of decreasing order of potential

Reason(R): Negative gradient of electric potential is electric field.

13  Assertion (A): A convex mirror cannot form real images.

Reason (R): Convex mirror converges the parallel rays that are incident on it.

14 Assertion(A): A convex lens of focal length 30 cm can’t be used as a simple microscope in normal setting.

Reason (R): For normal setting, the angular magnification of simple microscope is M=D/f

                                                 Section – B

Questions 15 and 16 are Case Study based questions and are

compulsory. Attempt any 4 sub parts from each question. Each 

question carries 1 mark.

15.   Faraday Cage: A Faraday cage or Faraday shield is an enclosure made of a conducting material. The fields within a conductor cancel out with any external fields, so the electric field within the enclosure is zero. These Faraday cages act as big hollow conductors you can put things in to shield them from electrical fields. Any electrical shocks the cage receives, pass harmlessly around the outside of the cage.

1. Which of the following material can be used to make a Faraday 

cage?

(i)

a)Plastic

b)Glass

c) Copper

d)Wood

2. Example of a real-world Faraday cage is 

a) car

b) plastic box

c) lightning rod

d) metal rod

3. What is the electrical force inside a Faraday cage when it is struck 

by lightning?

a) The same as the lightning

b) Half that of the lightning

c) Zero

d) A quarter of the lightning

4. An isolated point charge +q is placed inside the Faraday cage. Its 

surface must have charge equal to-

a) Zero

b) +q

c) –q

d) +2q

5. A point charge of 2C is placed at centre of Faraday cage in the shape 

of cube with surface of 9 cm edge. The number of electric field lines 

passing through the cube normally will be-

a) 1.9105 Nm2/C entering the surface

b) 1.9105 Nm2/C leaving the surface

c) 2.0105 Nm2/C leaving the surface

d) 2.0105 Nm2/C entering the surface

16 Sparking Brilliance of Diamond:

The total internal reflection of the light is used in polishing diamonds to 

create a sparking brilliance. By polishing the diamond with specific cuts, it 

is adjusted the most of the light rays approaching the surface are incident 

with an angle of incidence more than critical angle. Hence, they suffer 

multiple reflections and ultimately come out of diamond from the top. This 

gives the diamond a sparking brilliance. 

1. Light cannot easily escape a diamond without multiple internal 

reflections. This is because:

a) Its critical angle with reference to air is too large

b) Its critical angle with reference to air is too small

c) The diamond is transparent 

d) Rays always enter at angle greater than critical angle

2. The critical angle for a diamond is 24.4o

. Then its refractive index is-

a) 2.42

b) 0.413

c) 1

d) 1.413

3. The basic reason for the extraordinary sparkle of suitably cut

diamond is that

a) It has low refractive index

b) It has high transparency

c) It has high refractive index

d) It is very hard

4. A diamond is immersed in a liquid with a refractive index greater 

than water. Then the critical angle for total internal reflection will

 a) will depend on the nature of the liquid

 b) decrease

 c) remains the same

 d) increase

5. The following diagram shows same diamond cut in two different 

shapes.

The brilliance of diamond in the second diamond will be:

a) less than the first

b) greater than first

c) same as first

d) will depend on the intensity of light

                                           Section – C

All questions are compulsory. In case of internal choices, attempt 

anyone. 

17 Two straight infinitely long wires are fixed in space so that the current in the left wire is 2 A and directed out of the plane of the page and the current in the right wire is 3 A and directed into the plane of the page. In which 

region(s) is/are there a point on the x-axis, at which the magnetic field is 

equal to zero due to these currents carrying wires? Justify your answer.

18 Draw the graph showing intensity distribution of fringes with phase angle 

due to diffraction through single slit.

 OR

What should be the width of each slit to obtain n maxima of double slit 

pattern within the central maxima of single slit pattern?

19 Deduce an expression for the potential energy of a system of two point

charges q1 and q2 located at positions r1 and r2 respectively in an external 

field (E⃗ )

 OR

Establish the relation between electric field and electric potential at a 

point.

Draw the equipotential surface for an electric field pointing in +Z direction 

with its magnitude increasing at constant rate along –Z direction

20  Explain with help of circuit diagram, the action of a forward biased p-n 

junction diode which emits spontaneous radiation. State the least band gap 

energy of this diode to have emission in visible region.

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