A particle of mass M and charge Q moving with velocity describes a circular path of radius R when subjected to a uniform transverse magnetic field of induction B. The work done by the field when the particle completes one full circle is.
zero
BQ 2R
BQv 2R
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 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 electron is moving with velocity v in the direction of magnetic field B, then force acting on electron is
zero
e (v x B)
e (B x v)
200 J
A wire carrying current i and other carrying is in the same direction produce a magnetic field B at the midpoint. What will be the field when 2i current is switched off ?
B/2
2B
B
4B
C.
B
Magnetic field
Two particles A and B of masses m and 2m have charges q and 2q respectively. Both particles moving with velocities v1 and v2 respectively in the same direction and enter the same magnetic field B acting normally to their direction of motion. If the two forces FA and FB acting on them are in the ratio of 1 : 2, the ratio of their velocities is
2 : 1
3 : 2
2 : 3
1 : 1
A narrow beam of protons and deuterons, each having the same momentum, enters a region of uniform magnetic field directed perpendicular to their direction of momentum. The ratio of the radii of the circular paths described by them is
2 : 5
3 : 2
2 : 3
1 : 1
A horizontal overhead power line carries a current of 90 A in east to west direction. The magnitude and direction of the magnetic field due to the current 1.5 m below the line is
2.5 x 10-5 T towards north
3 x 10-5 T towards east
1.2 x 10-5 T towards south
1 x 10-5 T towards west
A galvanometer has a resistance of 30 Q. It gives full scale deflection with a current of 2mA. Calculate, the value of the resistance needed to convert it into an ammeter of range 0 − 0.3 A. The value of the resistance needed to convert galvanometer into ammeter
0.2 Ω
0.3 Ω
0.4 Ω
0.52 Ω