Punjab Physics 2021 — Solved Past Paper with Answers

Q1. Relation for energy density in case of an inductor is:

• A. A✓
• B. B
• C. C
• D. D

Explanation: This is a factual recall.Energy density = B2/2μo

Q2. The Lenz's law is also a statement of:

• A. Law of conservation of momentum
• B. Law of conservation of charge
• C. Law of conservation of energy✓
• D. Faraday's law

Explanation: Lenz law is also a statement of the law of conservation of energy that can be conveniently applied to the circuits involving induced currents.

Q3. Peak to Peak value of an alternating voltage is:

• A. A
• B. B
• C. C
• D. D✓

Explanation: Explanation will be added soon!

Q4. In RLC series resonance circuit, the condition for resonance is:

• A. XL=XC
• B. XL<XC
• C. XL>XC
• D. XL>Z✓

Explanation: Explanation will be added soon!

Q5. Young's modulus of lead is:

• A. 1.5x1019Nm-2
• B. 7.7x109 Nm-2
• C. 5.6x109 Nm-2
• D. 2.2x109Nm-2✓

Explanation: Explanation will be added soon!

Q6. Number of diodes used in half wave rectifier is:

• A. 4
• B. 3
• C. 2
• D. 1✓

Explanation: Explanation will be added soon!

Q7. S.I unit of current gain of transistor is:

• A. Coulomb
• B. Ampere
• C. Farad
• D. No unit✓

Explanation: Explanation will be added soon!

Q8. When platinum wire is heated, it appears cherry red at:

• A. 1300°C
• B. 1100°C
• C. 900°C
• D. 500°C✓

Explanation: Explanation will be added soon!

Q9. The value of Wein's constant is:

• A. 2.9x103mK
• B. 2.9x10-3mK
• C. 2.9mK
• D. 2.9x10-2mK✓

Explanation: Explanation will be added soon!

Q10. In Helium-Neon laser, the value of Helium is:

• A. 85%
• B. 75%
• C. 65%
• D. 60%✓

Explanation: Explanation will be added soon!

Q11. Half life of Uranium-238 is:

• A. 4.5x1012 years
• B. 4.5x1011 years
• C. 4.5x1010 years
• D. 4.5x109 years✓

Explanation: Explanation will be added soon!

Q12. The dead time of the counter is:

• A. ~10-7S
• B. ~10-6S
• C. ~10-5S
• D. ~10-4S✓

Explanation: Explanation will be added soon!

Q13. Unit of electric flux is:

• A. Nm2C-2
• B. Nm2C-1
• C. N-1m2C-1
• D. Nm-2C✓

Explanation: Explanation will be added soon!

Q14. Question is given below:

• A. μoI✓
• B. μoA
• C. μoB
• D. None of the above

Explanation: The following is the solution:

Q15. Reciprocal of resistance is:

• A. Capacitance
• B. Conductance
• C. Inductance
• D. Resistance✓

Explanation: Explanation will be added soon!

Q16. Lorentz force is given by.

• A. A
• B. B
• C. C
• D. D✓

Explanation: Explanation will be added soon!

Q17. A power line 10m high carries a current 200A. The magnetic field of the wire at the ground is:

• A. 4x10-6T
• B. 40x10-6T
• C. 4x10-4T
• D. 4x10-3T✓

Explanation: Explanation will be added soon!