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.
Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.
What is the ratio of heat generated in R and 2R
|
(a) 2 : 1 |
(b) 1 : 2 |
(c) 4 : 1 |
(d) 1 : 4 |
Soap bubble appears coloured due to the phenomenon of
|
(a) Interference |
(b) Diffraction |
(c) Dispersion |
(d) Reflection |
The torque on a bar magnet due to the earth's magnetic field is maximum when the axis of the magnet is
|
(a) Perpendicular to the field of the earth |
|
(b) Parallel to the vertical component of the earth's field |
|
(c) At an angle of 33o with respect to the N-S direction |
|
(d) Along the North-South (N-S) direction |
Voltmeters V1 and V2 are connected in series across a D.C. line. V1 reads 80 volts and has a per volt resistance of 200 ohms. V2 has a total resistance of 32 kilo ohms. The line voltage is
|
(a) 120 volts |
(b) 160 volts |
(c) 220 volts |
(d) 240 volts |
The electrons are emitted in the photoelectric effect from a metal surface
|
(a) Only if the frequency of the incident radiation is above a certain threshold value |
|
(b) Only if the temperature of the surface is high |
|
(c) At a rate that is independent of the nature of the metal |
|
(d) With a maximum velocity proportional to the frequency of the incident radiation |
A long copper tube of inner radius R carries a current i. The magnetic field B inside the tube is
|
(a) |
(b) |
(c) |
(d) Zero |
