Magnetism And Matter — Physics STD 12 Science — Question

2μF capacitance has potential difference across its two terminals 200 volts. It is disconnected with battery and then another uncharged capacitance is connected in parallel to it, then P.D. becomes 20 volts. Then the capacity of another capacitance will be

(a) 2 μF

(b) 4 μF

(c) 18 μF

(d) 10 μF

The magnitude of magnifying power of an astronomical telescope is 5, the focal power of its eyepiece is 10 diopters. The focal power of its objective (in diopters) is:

A particle moves along the X-axis as x = u(t - 2s) + a(t - 2s)².

1. The initial velocity of the particle is u.
2. The accelerati?n of the particle is a.
3. The acceleration of the particle is 2a.
4. At t = 2s particle is at the origin.

A charged particle q is shot towards another charged particle Q which is fixed, with a speed v. It approaches Q upto a closest distance r and then returns. If q were given a speed 2v, the closest distances of approach would be

(a) r

(b) 2r

(c) r/2

(d) r/4

Assertion :   Penetrating power of X-rays increases with the increasing the wavelength.

Reason    : The penetrating power of X-rays increases with the frequency of X-rays.

(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.

Three observers A, B and C measure the speed of light coming from a source to be  and . The observer A moves towards the source, the observer C moves away from the source with the same speed. The observer B stays stationary. the surrounding space is vacuum every where. Then

(a)

(b)

(c)

(d)

The strength and direction of the magnetic field depends on ..........

The measurement of voltmeter in the following circuit is

(a) 2.4 V

(b) 3.4 V

(c) 4.0 V

(d) 6.0 V

A photo cell is a device which: