Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

A point charge q is rotated along a circle in the electric field generated by another point charge Q. The work done by the electric field on the roatating charge in one complete revolution is:

1. Zero.
2. Positive.
3. Negative.
4. Zero if the charge Q is at the centre and nonzero otherwise.

Assertion : Radioactivity of  undecayed radioactive nuclei of half life of 50 days is equal to that of 1.2   number of undecayed nuclei of some other material with half life of 60 days  

Reason    : Radioactivity is proportional to half-life.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If the assertion and reason both are false.

A parallel-plate capacitor has plates of unequal area. The larger plate is connected to the positive terminal of the battery and the smaller plate to its negative terminal. Let Q₊ and Q_- be the charges appearing on the positive and negative plates respectively:

The lines of forces due to earth's horizontal component of magnetic field are

(a) Parallel straight lines	(b) Concentric circles
(c) Elliptical	(d) Parabolic

Direction of induced emf is determined by:

The dimensions of linear charge density is:

To form a composite 16Μf, 1000 V  capacitor from a supply of identical capacitors marked 8 μF, 250 V we require a minimum number of capacitors

(a) 40

(b) 32

(c) 8

(d) 2

What is the average binding energy per nucleon over a wide range?

A man with defective eyes cannot see distinctly object at the distance more than 60 cm from his eyes. The power of the lens to be used will be

(a) + 60 D

(b) – 60 D

(c) – 1.66 D

(d)

Energy of photon whose frequency is ,  will be

(a) 4.14

(b) 4.14

(c) 4.14

(d) 4.14