Atoms — Physics STD 12 Science — Question

A thin spherical conducting shell of radius R has a charge q. Another charge Q is placed at the centre of the shell. The electrostatic potential at a point p a distance   from the centre of the shell is

(a)

(b)

(c)

(d)

The inability of a lens to bring all the rays coming from a point object to focus at one single point is called:

A 6kHz sinusoidal voltage is applied to a series RC circuit. The frequency of the voltage across the resistor is.

Spherical aberration in a lens

(a) Is minimum when most of the deviation is at the first surface

(b) Is minimum when most of the deviation is at the second surface

(c) Is minimum when the total deviation is equally distributed over the two surface

(d) Does not depend on the above consideration

To compare magnetic moments of two magnets by vibration magnetometer, 'sum and difference method' is better because

(a) Determination of moment of inertia is not needed which minimises the errors

(b) Less observations are required

(c) Comparatively less calculations

(d) All the above

A compass needle will show which one of the following directions at the earth's magnetic pole

(a) Vertical	(b) No particular direction
(c) Bent at 45° to the vertical	(d) Horizontal

A parallel plate capacitor consists of two circular plates each of radius 12cm and separated by 5.0mm. The capacitor is being charged by an external source. The charging current is constant and is equal to 0.15A.The displacement current is:

Two sources are called coherent if they produce waves:

When air in a capacitor is replaced by a medium of dielectric constant K, the capacity: