Three charged particles are initially in position-1. They are free to move and they come to position-2, after some time. Let U1 and U2 be the electrostatic potential energies in position-1 and 2 then
U1 = U2
U2 U1
U2 > U1
U1 > U2
In L-R circuit the current increases to three - fourth of its maximum value in 4s, then the time constant of the circuit is
2 loge 2
The sensitiveness of a moving coil galvanometer can be increased by decreasing the
number of turns in the coils
area of the coil
magnetic field
couple per unit twist of the suspension
The material of wire of potentiometer is made of
copper
steel
manganin
aluminium
C.
manganin
The alloys constantan and manganin are traditionally used for the coils in resistance boxes, for rheostats and for the wires in potentiometers and metre bridges in the laboratory. They have high resistivity and low temperature coefficient of resistance, both of which make them suitable for the purpose.
A potential difference V is applied at the ends of a copper wire of length l and diameter d. On doubling only d, drift velocity
becomes two times
becomes half
does not change
becomes one-fourth
A steady current of 5 A is maintained for 45 min. During this time it deposits 4.572 g of zinc at the cathode of a voltmeter. ECE of zinc is
3.38 × 10-4 g/C
3.397 × 10-4 g/C
3.384 × 10-3 g/C
3.394 × 10-3 g/C
The earth's magnetic induction at a certain point is 7 x 10-5 Wb/m2. This is to be annuled by the magnetic induction at the centre of a circular conducting loop of radius 5 cm. The required current in the loop is
0.56 A
5.6 A
0.28 A
2.8 A
An astronomical telescope has a large aperture to
reduce spherical aberration
have high resolution
increase span of observation
have low dispersion
Which of the following is more close to a black body?
Black board paint
Green leaves
Black holes
Red roses