Electric Charges and Fields — Physics STD 12 Science — Question

Identify the factor on which the capacitance of a parallel plate capacitor does not depend.

In Boolean algebra A.B=Y implies the:

A potentiometer has uniform potential gradient across it.  Two cells connected in series (i) to support each other and (ii) to oppose each other are balanced over 6m and 2m respectively on the potentiometer wire.  The e.m.f.’s of the cells are in the ratio of

(a) 1 : 2

(b) 1 : 1

(c) 3 : 1

(d) 2 : 1

The equivalent resistance between P and Q in the given figure, is

(a) 50 W

(b) 40 W

(c) 30 W

(d) 20 W

A constant current of 2.8A exists in a resistor. The rms current is:

1. 2.8A.
2. About 2A.
3. 1.4A.
4. Undefined for a direct current.

The resistance  of a conductor varies with temperature t as shown in the figure. If the variation is represented by  = , then

(a) α  and  β are both negative	(b) α and β are both positive
(c) α is positive and β is negative	(d) α is negative and β are positive

Mark the correct options:

1. Gauss's law is valid only for symmetrical charge distributions.
2. Gauss's law is valid only for charges placed in vacuum.
3. The electric field calculated by Gauss's law is the field due to the charges inside the Gaussian surface.
4. The flux of the electric field through a closed surface due to all the charges is equal to the flux due to the charges enclosed by the surface.

When the N-pole of a bar magnet points towards the south and S-pole towards the north, the null points are at the

(a) Magnetic axis	(b) Magnetic centre
(c) Perpendicular divider of magnetic axis	(d) N and S poles

The waves which are electromagnetic in nature are: