Electromagnetic Waves — Physics STD 12 Science — Question

Two coils are placed close to each other. The mutual inductance of the pair of coils depends upon

(a) The currents in the two coils

(b) The rates at which currents are changing in the two coils

(c) Relative position and orientation of the two coils

(d) The materials of the wires of the coils

According to Gauss’ Theorem, electric field of an infinitely long straight wire is proportional to

(a) r

(b)

(c)

(d)

X-rays are produced in X-ray tube operating at a given accelerating voltage. The wavelength of the continuous X-rays has values from

(a) 0 to ∞

(b)   to ∞, where

(c) 0  to   where

(d)  to , where 0 <

The rate of disintegration of fixed quantity of a radioactive element can be increased by

(a) Increasing the temperature	(b) Increasing the pressure
(c) Chemical reaction	(d) It is not possible

One serious drawback of semi-conductor devices is:

When a bar magnet falls through a long hollow metal cylinder fixed with its axis vertical, the final acceleration of the magnet is

(a) Equal to zero

(b) Less than g

(c) Equal to g

(d) Equal to g in to beginning and then more than g

In a L - C - R circuit, as the frequency of an alternating current increases the impedance of the circuit.

When original mass of star is greater than 5 M (M = mass of the sun). The death of this star will give rise to

(a) White dwarf

(b) Black hole

(c) Quasars

(d) Nebula

and   ions having same kinetic energy pass through a region of space filled with uniform magnetic field B directed perpendicular to the velocity of ions. The masses of the ions  and  are respectively in the ratio 1 : 4 : 16. As a result

(a)  ions will be deflected most

(b)  and   ions will suffer same deflection

(c) All ions will suffer the same deflection

(d) a, b

When was Van de Graff generator invented and by whom?