Moving Charges and Magnetism — Physics STD 12 Science — Question

64 small drops of mercury, each of radius r and charge q coalesce to form a big drop. The ratio of the surface density of charge of each small drop with that of the big drop is

(a) 1 : 64

(b) 64 : 1

(c) 4 : 1

(d) 1 : 4

If 64 charged drops of water are mixed to form one big drop, then how many times the value of potential on the big drop will be from the full value?

In photoelectric effect, the K.E. of electrons emitted from the metal surface depends upon

(a) Intensity of light	(b) Frequency of incident light
(c) Velocity of incident light	(d) Both intensity and velocity of light

A virtual and enlarged image of the object forms:

Two point charges q₁ and q₂ are situated at a distance d. There is no such point in between them where the electric field is zero. What can we deduce?

The maximum distance upto which TV transmission from a TV tower of height h can be received is proportional to

(a) h1/2

(b) h

(c) h3/2

(d) h2

One watt is equal to __________?

The target used in a Coolidge tube for the production of X-rays is made up of ________ .

The internal resistance of a cell is the resistance of

(a) Electrodes of the cell	(b) Vessel of the cell
(c) Electrolyte used in the cell	(d) Material used in the cell

Assertion :  The poles of magnet cannot be separated by breaking into two pieces.

Reason     : The magnetic moment will be reduced to half when a magnet is broken into two equal pieces.

(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.