ISC 2015 Physics Question Paper for Class 12

About this paper

This is ISC Class 12 Physics Paper 1 (Theory), code 861A, from the 2015 CISCE board examination. It runs for three hours plus fifteen minutes of reading time and has two parts: Part I (20 marks) is a compulsory question of five multiple-choice items and fifteen brief answers, and Part II (50 marks) asks for ten five-mark questions, four from Section A, three from Section B and three from Section C. Section A covers electrostatics, current electricity, magnetism, induction and AC; Section B covers wave and ray optics; Section C covers photoelectric effect, atoms, nuclei and electronics. Several questions use printed figures, including a capacitor network, an LCR circuit and a photoelectric graph. Log tables may be used and useful constants are printed at the end.

Exam

ISC Class 12

Subject

Physics

Year

2015

Paper code

861A

Maximum marks

70

Time allowed

3 hours + 15 min reading

Questions

15

Pages

8

Answers included

No, questions only

Paper pattern

• Part I

  20 marks

  Question 1, compulsory: 5 multiple-choice items and 15 short answers

• Part II – Section A

  20 marks

  Questions 2–7, five marks each; answer any four

• Part II – Section B

  15 marks

  Questions 8–11, five marks each; answer any three

• Part II – Section C

  15 marks

  Questions 12–15, five marks each; answer any three

Topics covered

• Electric dipole and capacitors
• Current electricity and Wheatstone bridge
• Potentiometer
• Magnetism and earth's magnetic field
• Electromagnetic induction
• Alternating current and LCR circuits
• Electromagnetic waves
• Huygens' principle, interference and diffraction
• Lenses, mirrors and optical instruments
• Photoelectric effect and matter waves
• Bohr model, X-rays and radioactivity
• Rectifiers and logic gates

Questions from this paper

1. An emf of 2 V is induced in a coil when the current in it is changed from 0 A to 10 A in 0.40 s. Find the coefficient of self-inductance of the coil.
2. A 10 m long uniform wire of resistance 20 Ω is used as a potentiometer wire in series with a 480 Ω resistance and a 5 V battery of negligible internal resistance. If a cell's emf e is balanced across 6 m of the wire, calculate the potential gradient and the value of e.
3. On the basis of Huygens' wave theory of light, show that the angle of reflection is equal to the angle of incidence, with a labelled diagram.
4. Laser light of wavelength 630 nm falls on a pair of slits 1.8 mm apart, with the screen 80 cm away. Calculate the fringe width and the distance of the 10th bright fringe from the centre of the pattern.
5. On the basis of Bohr's theory, derive an expression for the radius of the nth orbit of the electron in a hydrogen atom.
6. Draw a labelled diagram of a full-wave rectifier and show how the output voltage varies with time for a sinusoidal input.