Electric intensity at a point varies as r-3 for ____.
a point charge
an electric dipole
a plane infinite sheet of charge
a line charge of infinite length
If a pellet carrying a charge of 0.5 coulomb is accelerated through a potential of 2000 volts, then it attains a kinetic energy equal to ____.
1000 joule
1000 ergs
1000 kilowatt-hours
500 ergs
Force between the two parallel wires carrying current has been used to define ____.
ampere
coulomb
volt
watt
The temperature coefficient of resistance of a wire is 0.00125 peroC. At 300 k, its resistance is I ohm. This resistance of the wire will be 2 ohm at.
1154oK
1100oK
1400oK
1127oK
A constant voltage is applied between the two ends of a uniform metallic wire. Some heat is developed in it. The heat developed is doubled if
Both the length and the radius of the wire are halved.
Both the length and the radius of the wire are doubled
The radius of the wire is doubled
The length of the wire is doubled
The electrostatic field due to a point charge depends on the distance r as Indicate which of the following quantities shows same dependence on r
Intensity of light from a point source.
Electrostatic potential due to a point charge.
Electrostatic potential at a distance r from the centre of a charged metallic sphere. Given r< radius of the sphere
None of these
A piece of copper and another of germanium are cooled from room temperature to 80oK. The resistance of
Each of them increases
Each of them decreases
Copper increases and germanium decreases
Copper decreases and germanium increases
A 4 (F capacitor, a resistance of 2.5 M( is in series with 12 V battery. Find the time after which the potential difference across the capacitor is 3 times the potential difference across the resistor. [Given In (2)= 0.693]
13.86s
6.93s
7s
1.4s
An ideal gas is filled in a closed rigid and thermally insulated container. A coil of 100 ( resistor carrying current I A for 5 minutes supplies heat to the gas. The change in internal energy of the gas is
10 kJ
30 KJ
20 KJ
0 KJ
A resistance of 2( is connected across one gap of a metrebridge (the length of the wire is 100 cm) and an unknown gap. When these resistances are interchanged, the balance point shift by 20 cm. Neglecting any corrections, the unknown resistance is
3(
4(
5(
6(