Electrostatics — Physics STD 12 Science — Question

Which of the following shows that the earth behaves as a magnet?

The reactance of a circuit is zero. It is possible that the circuit contains:

1. An inductor and a capacitor.
2. An inductor but no capacitor.
3. A capacitor but no inductor.
4. Neither an inductor nor a capacitor.

In a working nuclear reactor, Cadmium rods, (control rods) are used to

(a) Speed up neutrons	(b) Slow down neutrons
(c) Absorb some neutrons	(d) Absorb all neutrons

If L is the coherence length and c the velocity of light, the coherent time is

(a) cL

(b)

(c)

(d)

An ammeter and a voltmeter of resistance R are connected in series to an electric cell of negligible internal resistance. Their readings are A and V respectively.  If another resistance R is connected in parallel with the voltmeter

(a) Both A and V will increase	(b) Both A and V will decrease
(c) A will decrease and V will increase	(d) A will increase and V will decrease

Unit of induced emf is:

If the ionisation potential of helium atom is 24.6 volt, the energy required to ionise it will be

(a) 24.6 eV

(b) 24.6 V

(c) 13.6 V

(d) 13.6 eV

The 6563 Å line emitted by hydrogen atom in a star is found to be red shifted by 5 Å. The speed with which the star is receding from the earth is

(a) 17.29  × 109 m/s

(b) 4.29 × 107 m/s

(c) 3.39  × 105 m/s

(d) 2.29 ×  105 m/s

Silver and copper voltameter are connected in parallel with a battery of e.m.f. 12 V. In 30 minutes, 1 gm of silver and 1.8 gm of copper are liberated. The power supplied by the battery is ( and

(a) 24.13 J/sec

(b) 2.413 J/sec

(c) 0.2413 J/sec

(d) 2413 J/sec

The electric field lines are crowded where electric field is: