CBSE Class 12 Physics Board Exam 2026

(Board Pattern)

Time: 3 Hours
Maximum Marks: 70

SECTION A

(1 × 20 = 20 Marks)

Attempt all questions.

1. The SI unit of electric flux is:

(a) N/C

(b) Nm²/C

(c) C/N

(d) Nm

2. A capacitor of capacitance C is connected to a battery. If the distance between plates is doubled, the capacitance becomes:

(a) C

(b) 2C

(c) C/2

(d) 4C

3. Drift velocity of electrons is directly proportional to:

(a) Temperature

(b) Electric field

(c) Resistance

(d) Length of conductor

4. The magnetic field at the center of a circular loop carrying current is proportional to:

(a) I

(b) 1/R

(c) IR

(d) I/R

5. Lenz’s law is based on conservation of:

(a) Charge

(b) Energy

(c) Momentum

(d) Mass

6. RMS value of AC is equal to:

(a) V₀

(b) V₀/2

(c) V₀/√2

(d) √2V₀

7. In an ideal transformer:

(a) Output power > Input power

(b) Output power = Input power

(c) Output power < Input power

(d) Depends on load

8. The energy of a photon is given by:

(a) hλ

(b) hc/λ

(c) λ/h

(d) h/λ

9. In Young’s double slit experiment, fringe width depends on:

(a) Wavelength

(b) Distance between slits

(c) Distance to screen

(d) All of these

10. The refractive index of a medium is maximum for:

(a) Red

(b) Yellow

(c) Green

(d) Violet

11. Half-life of a radioactive substance depends on:

(a) Initial amount

(b) Temperature

(c) Pressure

(d) Decay constant

12. In forward bias of p-n junction:

(a) Depletion region widens

(b) Depletion region narrows

(c) No change

(d) Junction breaks

13. The binding energy per nucleon is maximum for:

(a) Hydrogen

(b) Iron

(c) Uranium

(d) Helium

14. In photoelectric effect, stopping potential depends on:

(a) Intensity

(b) Frequency

(c) Distance

(d) Area

15. If resistance increases with temperature, it is:

(a) Semiconductor

(b) Electrolyte

(c) Metal

(d) Insulator

16. The direction of magnetic field due to current is given by:

(a) Fleming’s Left Hand Rule

(b) Fleming’s Right Hand Rule

(c) Right Hand Thumb Rule

(d) Lenz’s Law

17. The focal length of convex mirror is always:

(a) Positive

(b) Negative

(c) Zero

(d) Infinite

18. In a series LCR circuit at resonance:

(a) XL > XC

(b) XL < XC

(c) XL = XC

(d) R = 0

19. The SI unit of magnetic flux is:

(a) Tesla

(b) Weber

(c) Henry

(d) Ampere

20. The work function is minimum for:

(a) Metal

(b) Insulator

(c) Semiconductor

(d) Gas

SECTION B

(2 × 7 = 14 Marks)

1. State Gauss’s Law.
2. Define electric dipole moment. Write its SI unit.
3. Derive relation between current and drift velocity.
4. Define magnetic dipole moment of a current loop.
5. What is self-induction? Write expression for self-induced emf.
6. State Huygens’ Principle.
7. Define half-life. Derive relation between half-life and decay constant.

SECTION C

(3 × 7 = 21 Marks)

1. Derive expression for capacitance of parallel plate capacitor.
2. Obtain expression for magnetic field at center of circular loop.
3. Explain working of AC generator with diagram.
4. Derive mirror formula using ray diagram.
5. Explain Einstein’s photoelectric equation.
6. Explain Bohr’s postulates of hydrogen atom.
7. Draw V-I characteristics of p-n junction diode and explain.

SECTION D (Case Study)

(4 × 1 = 4 Marks)

A student performs Young’s Double Slit Experiment using light of wavelength 600 nm.
The slit separation is 0.3 mm and screen distance is 1.5 m.

1. Write formula of fringe width.
2. Calculate fringe width.
3. What happens if wavelength increases?
4. Name the type of interference.

SECTION E

(5 × 2 = 10 Marks)

1. Derive expression for electric field due to infinite line charge.
2. Explain cyclotron with diagram and derive expression for cyclotron frequency.

SECTION F

(5 × 1 = 5 Marks)

1. Derive expression for de Broglie wavelength.