CBSE Sample Papers for Class 12 Physics Set 10 for Practice

Students must start practicing the questions from CBSE Sample Papers for Class 12 Physics with Solutions Set 10 are designed as per the revised syllabus.

CBSE Sample Papers for Class 12 Physics Set 10 for Practice

Time Allowed: 3 Hours
Maximum Marks: 70 Marks

General Instructions:

1. There are 35 questions in all. All questions are compulsory.
2. This question paper has five sections: Section A, Section B, Section C, Section D and Section E. All the sections are compulsory.
3. Section A contains eighteen MCQ of 1 mark each, Section B contains seven questions of two marks each, Section C contains five questions of three marks each, section D contains three long questions of five marks each and Section E contains two case study based questions of 4 marks each.
4. There is no overall choice. However, an internal choice has been provided in section B, C, D and E. You have to attempt only one of the choices in such questions.
5. Use of calculators is not allowed.

Section – A (18 Marks)

Question 1.
Which of the following combinations should be selected for better tuning of given circuit used for communication? [1]

(a) R = 20Ω, L = 1.5H, C = 35µF
(b) R = 25Ω, L = 2.5H, C = 45µF
(c) R = 15Ω, L = 3.5H, C = 30µF
(d) R = 25Ω, L = 1,51-1, C = 45µF

Question 2.
The two sources of light said to be coherent, if they: [1]
(a) have zero phase difference
(b) have constant phase difference
(c) have phase difference
(d) both (a) and (b)

Question 3.
The conditions for the given phenomenon to occur is: [1]

(a) ∠i = ∠r
(b) ∠i = ∠c
(c) ∠i < ∠c (d) ∠i > ∠c

Question 4.
If we double the length of a conducting wire keeping its radius and potential difference across the resistor same, then for the same interval of time, by the factor the heat generated across the conductor will be changed is: [1]
(a) \(\frac{\mathrm{H}}{4}\)
(b) \(\frac{\mathrm{H}}{2}\)
(c) \(\frac{\mathrm{H}}{8}\)
(d) H

Question 5.
In a constant and vertically upward directed electric field E, an electron falls from rest across a vertical distance h. The direction of the electric field is now reversed but the magnitude remains unchanged. It permits a proton to fall from rest through the same vertical distance h. The electron’s time of fall is proportional to the proton’s time of fall is: [1]
(a) Smaller
(b) 5 times bigger
(c) 10 times bigger
(d) equal

Question 6.
Which part of the electromagnetic spectrum is used for detecting fake currency notes? [1]
(a) UV-rays
(b) x-rays
(c) y-rays
(d) All of these

Question 7.
A diode is in forward bias if. [1]
(a) positive end is connected to p-side
(b) negative end is connected to n-side
(c) Both (a) and (b)
(d) None of the above

Question 8.
The given object; magnifying power of given object depend upon: [1]
(a) colour of light
(b) focal length
(c) magnification
(d) All of these

Question 9.

What is the ratio of radii of the orbits corresponding to first excited state and ground state in a hydrogen atom? [1]
(a) 1: 2
(b) 2 : 1
(c) 1: 4
(d) 4 : 1

Question 10.
Two nuclei have mass number in the ratio 3:5. The ratio of their nuclear densities: [1]
(a) 3 : 5
(b) 5 : 3
(c) 2 : 1
(d) 1 : 1

Question 11.
The first minima for red light having a wavelength of 660 nm coincide with the first maxima of some other wavelength in a single slit diffraction experiment. The unknown value of wavelength is: [1]
(a) 400 nm
(b) 350 nm
(c) 300 nm
(d) 440 nm

Question 12.
The V-I characteristics of a silicon diode is shown in the figure. The resistance of the diode at I_D = 15 mA is: [1]

(a) 12 Ω
(b) 20 Ω
(c) 10 Ω
(d) 5 Ω

Question 13.
Which of following has high conductivity? [1]
(a) Semiconductors
(b) insulators
(c) metals
(d) Non-metal

Question 14.
Monochromatic light of wavelength 667 nm is produced by a helium neon laser. The power emitted is 9 mW. The number of photons arriving per second on the average at a target irradiated by this beam is: [1]
(a) 3 × 10¹⁶
(b) 3 × 10¹⁵
(c) 3 × 10¹⁹
(d) 3 × 10^17</sup

Question 15.
Region without free electrons and holes in a p-n junction is: [1]
(a) n-region
(b) p-region
(c) depletion region
(d) none of these
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 and 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.

Question 16.
Assertion (A): Electromagnetic radiations exert pressure.
Reason (R): EM-waves carry both momentum and energy. [1]

Question 17.
Assertion (A): In Young’s double slit experiment interference
pattern disappears when one of the slits is closed.
Reason (R): Interference occurs due to super-imposition of light wave from two coherent sources. [1]

Question 18.
Assertion (A): Photoelectric effect demonstrates the wave nature of light.
Reason (R): The number of photo-electrons is directly proportional to the frequency of light. [1]

Section – B

Question 19.
How are infrared waves produced? Write some important uses of IR waves. [2]
OR
Explain how a microwave oven works to heat up a food item containing water molecules kept in it.

Question 20.
Explain the following: [2]
(A) Why do magnetic lines of force form continuous closed loops?
(B) Why are the field lines repelled (expelled) when a diamagnetic material is placed in an external uniform magnetic field?

Question 21.
A device X is connected to an alternating source V = V₀ sin ωt. The variation of voltage, current and power in one cycle is shown in the following figure. Which curve shows power consumption over a full cycle?

Question 22.
Give reason for the following : [2]
The mass of a nucleus in its ground state is always less than the total mass of its constituent’s neutrons and protons. Explain.
OR
A proton and an alpha particle are accelerated through the same potential. Which one will have less kinetic energy? Give reasons to justify your answer.

Question 23.
(A) What do you mean by atomic mass unit? [2]
(B) Calculate the energy equivalent of 1 g substance. [2]

Question 24.
The radius of the innermost electron orbit of a hydrogen atom is 5.3 × 10^-11 m. What are the radius of the n = 2 and n = 3 orbits? [2]

Question 25.
A battery of emf 6 V and internal resistance 2Ω is connected to a resistor. If the current in the circuit is 0.25 A, find: [2]
(A) the resistance of the resistors;
(B) the terminal voltage of the battery. 2

Section – C (15 Marks)

Question 26.
Show that when a current is divided between two resistance by following Kirchoff’s laws, the total heat generated across those resistance will be the minimum. [3]

Question 27.
What is the effect of change in temperature in case of conductors and semiconductors? Explain briefly with the help of energy band diagrams while explaining the distinguishing characteristics. [3]

Question 28.
(A) When do we say that the magnetic flux is  [3]

1. positive
2. negative?
   (B) Predict the direction of induced current in the following situations:

OR
Derive an expression for the mutual inductance of two long co-axial solenoids of same length wound over one another.

Question 29.
What is Einstein’s mass-energy equivalence principle? What is its importance? State the law of conservation of mass-energy. [3]
OR
(A) When an electron in a hydrogen atom jumps from the third excited state to the ground state, what would be the change in the deBroglie’s wavelength associated with an electron? Justify your answer.
(B) What is the shortest wavelength present in the Paschen series of spectral line?

Question 30.
If the refractive index of the glass is \(\sqrt{3}\), calculate the value of angle of emergence from the prism by tracing the path of light after passing through the prism. [3]

Section – D (15 Marks)

Question 31.
(A) Draw a labelled ray diagram for the formation of image by a compound microscope. [5]
(B) What is the mathematical expression for the magnification of a compound microscope?
(C) For a compound microscope, both objective and eyepiece should have short focal lengths. Justify.
OR
(A) How is the working of a telescope different from that of a microscope?
(B) The focal lengths of the objective and eye-piece of microscope are 1.25 cm and 5 cm respectively.
Find the position of the object relative to the objective in order to obtain an angular magnification of 30 in normal adjustment.

Question 32.
(A) Define electrostatic potential difference between two points. Write its SI unit. What is the amount of work done in arranging the system of charges as shown in figure? [5]

(B) What do you mean by equipotential surfaces?
(C) If we force a charge to move along a equipotential surface, then how much work will be done? Explain.
OR
(A) Derive an expression for energy stored per unit volume in a parallel plate capacitor with the help of a diagram.
(B) If we introduce a dielectric medium in between those two parallel plate, then what will happen to its capacitance?
(C) But if we introduce a conductor in between those two parallel plate, then what will happen to its capacitance?

Question 33.
(A) State Ampere’s circuital law.
(B) Use this law to obtain the expression for the magnetic field inside an air cored solenoid having ‘n’ turns per unit length and carrying a steady current T.
(C) Draw the pattern of magnetic field lines for a solenoid.
OR
(A) An electron moves around the nucleus in a hydrogen atom of radius 0.51 A, with a velocity of 2 × 10⁵ m/s. Calculate the following:

1. the equivalent current due to orbital motion of electron.
2. the magnetic field produced at the centre of the nucleus.
3. the magnetic moment associated with the electron.

(B) A square loop of side 20 cm carrying current of 1 A is kept near an infinite long straight wire carrying a current of 2 A in the same plane as shown in the figure. Find out the direction and magnitude of the net resultant force on the square loop due to the infinite long straight wire.

Section – E (8 Marks)

Question 34.

The touch screen on a mobile phone, an MP3 player, or (as shown here) a medical device uses the physics of capacitors. Behind the screen are two parallel layers, one behind the other, of thin strips of a transparent conductor such as indium tin oxide. A voltage is maintained between the two layers.

The strips in one layer are oriented perpendicular to those in the other layer; the points where two strips overlap act as a grid of capacitors. When you bring your finger (a conductor) up to a point on the screen, your finger and the front conducting layer act like a second capacitor in series at that point. The circuitry attached to the conducting layers detects the location of the capacitance change, and so detects where you touched the screen.

(A) Two metal plates form a parallel plate capacitor. The distance between the plates is d. A metal sheet of thickness d/2 and of the same area is introduced between the plates. What is the ratio of the capacitance in the two cases? [1]
(B) Net capacitance of three identical capacitors in series is 1 μF. What will be their net capacitance if connected in parallel? [1]
(C) A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. What is the total electrostatic energy of the resulting system? [2]
OR
A parallel plate condenser is connected with the terminals of a battery. The distance between the plates is 6 mm. If a glass plate (dielectric constant, K = 9) of 4.5 mm thickness is introduced between them, then find the change is the capacity.

Question 35.
The diagnostic technique called MR.I, or magnetic resonance imaging requires a magnetic field of about 1.5 T. In a typical MRI scan, the patient lies inside a coil that produces the intense field. The currents required are very high, so the coils are bathed in liquid helium at a temperature of 4.2 K to keep them from overheating.

(A) A rectangular loop carrying a current i is situated near a long straight wire such that the wire is parallel to the one of the sides of the loop and is in the plane of the loop. If a steady current I is established in wire as shown in figure. Identify the motion of loop. [1]

(B) A charged particle is moving on circular path with velocity v in a uniform magnetic field B, if the velocity of the charged particle is doubled and strength of magnetic field is halved, then find the change in radius. [1]
(C) Biot-Savart law indicates that the moving electrons (velocity v) produce a magnetic field B. Give the relation between them.

OR
An electron is projected with uniform velocity along the axis of a current carrying long solenoid. What do you conclude with this statement? [2]