Indicate which one of the following system is digital
|
(a) Pulse position modulation |
(b) Pulse code modulation |
|
(c) Pulse width modulation |
(d) Pulse amplitude modulation |
(b) Pulse code modulation
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The work function of metal is 1 eV. Light of wavelength 3000 Å is incident on this metal surface. The velocity of emitted photo-electrons will be
|
(a) 10 m/sec |
(b) 1 |
(c) |
(d) |
The two metallic plates of radius r are placed at a distance d apart and its capacity is C. If a plate of radius r/2 and thickness d of dielectric constant 6 is placed between the plates of the condenser, then its capacity will be
|
(a) 7C/2 |
(b) 3C/7 |
(c) 7C/3 |
(d) 9C/4 |
If the potential difference applied across X-ray tube is V volts, then approximately minimum wavelength of the emitted X-rays will be
|
(a) |
(b) |
(c) |
(d) |
An electric wire is connected across a cell of e.m.f. E. The current I is measured by an ammeter of resistance R. According to ohm's law
|
(a) |
(b) E = IR |
(c) E = R/I |
(d) E = I/R |
Two conducting spheres of radii 5 cm and 10 cm are given a charge of 15 μC each. After the two spheres are joined by a conducting wire, the charge on the smaller sphere is
|
(a) 5 μC |
(b) 10 μC |
(c) 15 μC |
(d) 20 μC |
Heavy water is used as moderator in a nuclear reactor. The function of the moderator is
|
(a) To control the energy released in the reactor |
|
(b) To absorb neutrons and stop chain reaction |
|
(c) To cool the reactor faster |
|
(d) To slow down the neutrons to thermal energies |
Substances in which the magnetic moment of a single atom is not zero, is known as
|
(a) Diamagnetism |
(b) Ferromagnetism |
(c) Paramagnetism |
(d) Ferrimagnetism |
