If an alternating voltage is represented as E = 141 sin (628 t), then the rms value of the voltage and the frequency are respectively
141 V, 628 Hz
100 V, 50 Hz
100 V, 100 Hz
141 V, 100 Hz
A step-down transformer is used on a 1000 V line to deliver 20 A at 120 V at the secondary coil. If the efficiency of the transformer is 80%, the current drawn from the line is
3 A
30 A
0.3 A
2.4 A
Band spectrum is also called
molecular spectrum
atomic spectrum
flash spectrum
line absorption spectrum
A fish at a depth of 12 cm in water is viewed by an observer on the bank of a lake. To what height the image of the fish is raised ?
9 cm
12 cm
3.8 cm
3 cm
A ray of light is incident at 50° on the middle of one of the two mirrors arranged at an angle of 60° between them. The ray then touches the second mirror, gets reflected back to the first mirror, making an angle of incidence
50°
60°
70°
80°
In a compound microscope, the intermediate image is
virtual, erect and magnified
real, erect and magnified
real, inverted and magnified
virtual, erect and reduced
A ray of light passes through an equilateral prism such that an angle of incidence is equal to the angle of emergence and the latter is equal to th the angle of prism. The angle of deviation is
45°
39°
20°
30°
C14 has half-life 5700 yr. At the end of 11400 yr, the actual amount left is
0.5 of original amount
0.25 of original amount
0.125 of original amount
0.0625 of original amount
The ionization potential of hydrogen is 13.6 V. The energy required to remove an electron from the second orbit of hydrogen is
3.4 eV
6.8 eV
13.6 eV
1.51 eV
A.
3.4 eV
The depletion layer of a p-n junction
is of constant width irrespective of the bias
acts like an insulating zone under reverse bias
has a width that increases with an increase in forward bias
is depleted of ions