Class 12 Physics Model Paper MCQs Test

1. The half-life of ₃₈Sr⁹¹ is 9.70 hours. What is the decay constant?

2. Two charges q1 and q2 are placed in a vacuum at a distance d and force between them is F. If a medium of relative permittivity 4 is introduced between them, then the new force will be:

3. The speed of electrons in the 2nd Bohr orbit is:

4. A closed surface encloses two equal and opposite charges. The net flux through the surface is:

5. A wire has a resistance of 12Ω. It is bent in the form of a circle. The effective resistance between the two points on any diameter of the circle is:

6. Photon A has twice the energy to that of photon B. The ratio of momentum of A and B is PA/PB = ______

7. When a battery of emf “E” and internal resistance “r” is connected across external resistance R, the power consumed in R is maximum when r⁄R is:

8. If the forward voltage in a diode is increased, the width of the depletion region:

9. The velocity at which the relativistic length of a body reduces to half of its original length is:

10. At what frequency an inductor of 1H will have a reactance of 500 ohms?

11. A consequence of Einstein’s theory of relativity is:

12. Two identical circular loops A and B of a metal wire are placed on a table without touching each other. Loop A carries a current which increases with time. In response, the loop B will:

13. The ratio of minimum to maximum wavelength in Balmer series is:

14. If input power and output power of an electric motor are 540 W and 382 W respectively. Then the efficiency is:

15. 1Henry = _________:

16. The constant α of a transistor is 0.95. What would be the change in the collector current corresponding to a change of 0.4mA in the base current in a common-emitter arrangement?

17. Two charges q1 and q2 are placed in a vacuum at a distance d and force between them is F. If a medium of relative permittivity 4 is introduced between them, then the new force will be: