In an electron gun the control grid is given a negative potential relative to cathode in order to
|
(a) Decelerate electrons |
|
(b) Repel electrons and thus to control the number of electrons passing through it |
|
(c) To select electrons of same velocity and to converge them along the axis |
|
(d) To decrease the kinetic energy of electrons |
(b) Repel electrons and thus to control the number of electrons passing through it
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A fully charged capacitor has a capacitance ‘C’. It is discharged through a small coil of resistance wire embedded in a thermally insulated block of specific heat capacity ‘s’ and mass ‘m’. If the temperature of the block is raised by ‘ ∆T ’, the potential difference ‘V’ across the capacitance is
|
(a) |
(b) |
(c) |
(d) |
If the direction of the initial velocity of the charged particle is neither along nor perpendicular to that of the magnetic field, then the orbit will be
|
(a) A straight line |
(b) An ellipse |
(c) A circle |
(d) A helix |
When N-type of semiconductor is heated
|
(a) Number of electrons increases while that of holes decreases |
|
(b) Number of holes increases while that of electrons decreases |
|
(c) Number of electrons and holes remains same |
|
(d) Number of electrons and holes increases equally |
Dispersion can take place for
|
(a) Transverse waves only but not for longitudinal waves |
|
(b) Longitudinal waves only but not for transverse waves |
|
(c) Both transverse and longitudinal waves |
|
(d) Neither transverse nor longitudinal waves |
When a magnetic substance is heated, then it
|
(a) Becomes a strong magnet |
(b) Losses its magnetism |
|
(c) Does not effect the magnetism |
(d) Either (a) or (c) |
Three long, straight parallel wires carrying current, are arranged as shown in figure. The force experienced by a 25 cm length of wire C is
|
(a) 10-3 N |
(b) 2.5 ×10-3 N |
(c) Zero |
(d) 1.5 × 10-3 N |
