Electric Charges and Fields — Physics STD 12 Science — Question

Assertion  :   A domestic electrical appliance, working on a three pin will continue working even if the top pin is removed.

Reason     : The third pin is used only as a safety device.

(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 dielectric slab is inserted between the plates of a capacitor. The charge on the capacitor is Q and the magnitude of the induced charge on each surface of the dielectric is Q':

1. Q' may be larger than Q.
2. Q' must be larger than Q.
3. Q' must be equal to Q.
4. Q' must be smaller than Q.

A circular coil of diameter 7cm has 24 turns of wire carrying current of 0.75A. The magnetic moment of the coil is

(a) 6.9	(b) 2.3
(c)	(d)

A body falling vertically downwards under gravity breaks in two parts of unequal masses. The centre of mass of the two parts taken together shifts horizontally towards:

1. Heavier piece.
2. Lighter piece.
3. Does not shift horizontally.
4. Depends on the vertical velocity at the time of breaking.

The maximum illumination on a screen at a distance of 2 m from a lamp is 25 lux. The value of total luminous flux emitted by the lamp is

(a) 1256 lumen

(b) 1600 lumen

(c) 100 candela

(d) 400 lumen

The state of charge inside a closed surface is changed in such a way that total charge remains constant, the flow of electric flux from the closed surface:

Consider a radioactive material of half-life 1.0 minute. If one of the nuclei decays now, the next one will decay

(a) After 1 minute

(b) After   minute

(c) After  minute, where N is the number of nuclei present at that moment

(d) After any time

How are the field lines in a uniform magnetic field ?

A wire of length 1 m is moving at a speed of 2ms^–1 perpendicular to its length and a homogeneous magnetic field of 0.5 T. The ends of the wire are joined to a circuit of resistance 6 W. The rate at which work is being done to keep the wire moving at constant speed is

(a)

(b)

(c)

(d) 1W