Two changes +q and -q are attached to the two ends of a light rod of length L, as shown in figure. The system is given a velocity ν perpendicular to magnetic field . The magnetic force on the system of charges and magnitude of force on one charge by the rod, are respectively
zero, zero
zero, qvB
2qvB, 0
2qvB, qvB
The intensity of magnetic field due to an isolated pole of strength mp at a point distant r from it will be
mp/r2
mp r2
r2/ mp
mp/r
A bulb and a condenser are connected in with an A>C source. On increasibg the frequency will
increase
decrease
sometimes increase and sometimes decrease
neither increase nor decrease.
The ratio of magnetic fields on the axis of a circular current carrying coil of radius a to the magnetic field at its centre will be
A charge q is uniformly distributed on a ring of radius r. A sphere of an equal radius is constructed with its centre lying on the periphery of the ring. The flux of electric field through the surface of the sphere will be
C.
Charge on ring q,
centre of ring = O
Centre of sphere = O'
Linear charge density of ring
λ =
Charge on arc AB of ring
qAB = λ ( arc AB )
=
qAB =
i.e Charged enclosed by sphere =
∴ Flux coming out of sphere =
When 100 V d.c is applied across a coil, a current of 1 A nows through it. When 100 V a.c. of 50 Hz is applied to the same coil only 0.5 A flows. The inductance of the coil is
0.55 H
5.5 H
0.55 mH
55 mH
A bulb of 25 W. 200 V and another bulb of 100 W, 200 V are connected in series with a supply line of 220 V. Then
both bulbs will glow with same brightness
both bulbs will get fused
25 W bulb will glow more brightly
100 W bulb will glow more brightly