Atoms — Physics STD 12 Science — Question

What happens to the force between magnetic poles when their pole strength and the distance between them are both doubled(a) Force increases to two times the previous value(b) No change(c) Force decreases to half the previous value(d) Force increases to four times the previous value

Assertion : Short wave bands are used for transmission of ratio waves to a large distance
Reason    : Short waves are reflected by ionosphere(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 assertion is false but reason is true.

A source of e.m.f. E = 15 V and having negligible internal resistance is connected to a variable resistance so that the current in the circuit increases with time as i = 1.2 t + 3. Then, the total charge that will flow in first five second will be(a) 10 C(b) 20 C(c) 30 C(d) 40 C

A barometer kept in an elevator reads 76cm when it is at rest. If the elevator goes up with increasing speed, the reading will be:

1. zero.
2. 76cm.
3. < 76cm.
4. > 76cm.

Curies law can be written as

An e.m.f. of 5 volt is produced by a self inductance, when the current changes at a steady rate from 3 A to 2 A in 1 millisecond. The value of self inductance is(a) Zero(b) 5 H(c) 5000 H(d) 5 mH

If a charged particle kept at rest experiences an electromagnetic force: