Current Electricity — Physics STD 12 Science — Question

Kinetic energy of emitted cathode rays is dependent on

(a) Only voltage

(b) Only work function

(c) Both (a) and (b)

(d) It does not depend upon any physical quantity

A moving coil galvanometer has N number of turns in a coil of effective area A, it carries a current I. The magnetic field B is radial. The torque acting on the coil is:

The part of a transistor which is heavily doped to produce a large number of majority carriers, is

(a) Base

(b) Emitter

(c) Collector

(d) None of these

Specific rotation of sugar solution is 0.01 SI units. 200  of impure sugar solution is taken in a polarimeter tube of length 0.25m and an optical rotation of 0.4rad is observed. The percentage of purity of sugar is the sample is

(a) 80%

(b) 89%

(c) 11%

(d) 20%

In an LCR circuit, capacitance is changed from C to 2C. For the resonant frequency to remain unchanged, the inductance should be changed from L to:

A thin prism  with angle 6° and made from glass of refractive index 1.54 is combined with another thin prism P₂ of refractive index 1.72 to produce dispersion without deviation. The angle of prism   will be

(a) 5° 24’

(b) 4° 30’

(c) 6°

(d) 8°

The magnetic flux linked with a coil, in webers, is given by the equations  ∅ =  Then the magnitude of induced e.m.f. at t = 2 second will be

(a) 2 volt

(b) 4 volt

(c) 8 volt

(d) 16 volt

Number of spectral lines in hydrogen atom is    

(a) 3

(b) 6

(c) 15

(d) Infinite

The continuous X-rays spectrum produced by an X-ray machine at constant voltage has

(a) A maximum wavelength	(b) A minimum wavelength
(c) A single wavelength	(d) A minimum frequency