ISC 2020 Physics Question Paper for Class 12

About this paper

This is ISC Class 12 Physics Paper 1 (Theory) from the 2020 board examination, with a worked answer printed after each question. It carries 70 marks, runs for three hours plus fifteen minutes of reading time, and has 22 compulsory questions in four sections. Section A is a twelve-mark question with five multiple-choice items and seven very short answers; Sections B and C have internal choices in two questions each, and each five-mark question in Section D has an internal choice. Numericals include drift speed, mutual inductance, the binding energy of oxygen-16, a potentiometer circuit and a series LCR circuit. A simple scientific calculator is allowed. The answers are not an official CISCE marking scheme, and a few of them contain errors.

Exam

ISC Class 12

Subject

Physics

Year

2020

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

22

Pages

8

Answers included

Yes

Paper pattern

• Section A

  12 marks

  Question 1: 5 multiple-choice and 7 very short answer parts, one mark each

• Section B

  22 marks

  Questions 2–12, two marks each; internal choice in two questions

• Section C

  21 marks

  Questions 13–19, three marks each; internal choice in two questions

• Section D

  15 marks

  Questions 20–22, long answers of five marks each, each with an internal choice

Topics covered

• Electrostatics and Gauss's theorem
• Capacitors and dielectrics
• Current electricity, Kirchhoff's laws and potentiometer
• Moving charges and magnetism
• Magnetic properties of materials
• Electromagnetic induction and alternating current
• Ray optics, lenses and microscopes
• Wave optics, diffraction and polarisation
• Dual nature of matter
• Atoms, nuclei and radioactivity
• Semiconductor devices and logic gates
• Communication systems

Questions from this paper

1. A uniform copper wire with a cross-sectional area of 1 mm² carries a current of 5 A. Calculate the drift speed of the free electrons in it (free electron number density of copper = 2 × 10²⁸ m⁻³).
2. When the current through one coil changes from 0 A to 15 A in 0.2 s, an emf of 750 V is induced in an adjacent coil. Calculate the coefficient of mutual inductance of the two coils.
3. Calculate the binding energy of the oxygen nucleus ¹⁶O, given: mass of a proton = 1.007825 u, mass of a neutron = 1.008665 u and mass of ¹⁶O = 15.994915 u.
4. A 400 Ω resistor, a 3 H inductor and a 5 μF capacitor are connected in series to a 220 V, 50 Hz ac source. Calculate the impedance of the circuit and the current flowing through it.
5. Draw the energy level diagram of the hydrogen atom and show the transitions responsible for the absorption lines of the Lyman series and the emission lines of the Balmer series.
6. Show with the help of a diagram how you will obtain an AND gate using only NAND gates.