Explanation:
You must know the working of an electron gun.
In an electron gun the control grid is given a negative potential relative to cathode in order to repel electrons and thus to control the number of electrons passing through it.
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Two coils of self inductance 
and 
are placed closer to each other so that total flux in one coil is completely linked with other. If M is mutual inductance between them, then
|
(a) |
(b) |
(c) |
(d) |
A wire of resistor R is bent into a circular ring of radius r. Equivalent resistance between two points X and Y on its circumference, when angle XOY is a, can be given by
|
(a) |
(b) |
(c) R (2 p – a) |
(d) |
The binding energy of deuteron 
is 1.112 MeV per nucleon and an α - particle 
has a binding energy of 7.047 MeV per nucleon. Then in the fusion reaction 
the energy Q released is
|
(a) 1 MeV |
(b) 11.9 MeV |
(c) 23.8 MeV |
(d) 931 MeV |
For sky wave propagation of a 10 MHz signal, what should be the minimum electron density in ionosphere
|
(a) ~ 1.2 × 1012 m–3 |
(b) ~ 106 m–3 |
(c) ~ 1014 m–3 |
(d) ~ 1022 m–3 |
The field normal to the plane of a wire of n turns and radius r which carries a current i is measured on the axis of the coil at a small distance h from the centre of the coil. This is smaller than the field at the centre by the fraction
|
(a) |
(b) |
(c) |
(d) |
