Electrostatic Potential and Capacitance — Physics STD 12 Science — Question

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

Binary of decimal number 25 is :

In Fresnel diffraction, if the distance between the disc and the screen is decreased, the intensity of central bright spot will

(a) Increase

(b) Decrease

(c) Remain constant

(d) None of these

How many number of electrons are present in -1C of charge:

In conductor when electrons move between two collisions, their paths are ... A... when external fields are absent and ... B...when external filed is present. Here, A and B refer to:

Crystal structure is studied by:

Two point charges +9e and +e are at 16 cm away from each other. Where should another charge q be placed between them so that the system remains in equilibrium

(a) 24 cm from +9e

(b) 12 cm from +9e

(c) 24 cm from +e

(d) 12 cm from +e

A piece of wood is taken deep inside a long column of water and released. It will move up:

1. With a constant upward acceleration.
2. With a decreasing upward acceleration.
3. With a deceleration.
4. With a uniform velocity.

An iron rod of volume   and relative permeability 1000 is placed inside a long solenoid wound with 5 turns/cm. If a current of 0.5 A is passed through the solenoid, then the magnetic moment of the rod is

(a) 10

(b) 15

(c) 20

(d) 25

A 60 watt bulb carries a current of 0.5 amp. The total charge passing through it in 1 hour is           

(a) 3600 coulomb

(b) 3000 coulomb

(c) 2400 coulomb

(d) 1800 coulomb