Electromagnetic Waves — Physics STD 12 Science — Question

A coil of self inductance 50 henry is joined to the terminals of a battery of e.m.f. 2 volts through a resistance of 10 ohm and a steady current is flowing through the circuit. If the battery is now disconnected, the time in which the current will decay to 1/e of its steady value is

(a) 500 seconds

(b) 50 seconds

(c) 5 seconds

(d) 0.5 seconds

A parallel beam of fast moving electrons is incident normally on a narrow slit. A fluorescent screen is placed at a large distance from the slit. if the speed of the electrons is increased , which of the following statements is correct?

The voltage gain of a triode depends upon

(a) Filament voltage

(b) Plate voltage

(c) Plate resistance

(d) Plate current

If A and B are two inputs in AND gate, then AND gate has an output of 1 when the values of A and B are

(a) A = 0, B = 0

(b) A = 1, B = 1

(c) A = 1, B = 0

(d) A = 0, B = 1

If the operating potential of an X-ray tube is 50 kV, the velocity of X-rays coming out of it is

(a) 4

(b) 3

(c)

(d) 3 m/s

A thin metal plate P is inserted half way between the plates of a parallel plate capacitor of capacitance C in such a way that it is parallel to the two plates. The capacitance now becomes

(a) C

(b) C/2

(c) 4C

(d) None of these

Colours of thin films result from

(a) Dispersion of light

(b) Interference of light

(c) Absorption of light

(d) Scattering of light

Electron-volt (eV) is the measure of:

In the formation of primary rainbow, the sunlight rays emerge at minimum deviation from rain-drop after

(a) One internal reflection and one refraction

(b) One internal reflection and two refractions

(c) Two internal reflections and one refraction

(d) Two internal reflections and two refractions