Moving Charges and Magnetism · Question 58

Charge q is uniformly spread on a thin ring of radius R. The ring rotates about its axis with a uniform frequency f Hz. The magnitude of magnetic induction at the center of the ring is

1. 0 q f2 R
2. 0 q f2R
3. 0 q2fR
4. 0 q2 f R

A galvanometer has a coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is to work as a voltmeter of 30 volt range, the resistance required to be added will be

1. 900
2. 1800
3. 500
4. 1000

A galvanometer has a coil of resistance 100 ohm and gives a full scale deflection for 30 mA current. If it is to work as a voltmeter of 30 volt range, the resistance required to be added will be

1. 900
2. 1800
3. 500
4. 1000

A square current carrying loop is suspended in a uniform magnetic field acting in the plane of the loop. If the force on one arm of the loop is F, the net force on the remaining three arms of the loop is

1. 3 F
2. - F
3. -3 F
4. F

A beam of cathode rays is subjected to crossed electric (E) and magnetic fields (B). The fields are adjusted such that the beam is not deflected. The specific charge of the cathode rays is given by (Where V is the potential difference between cathode and anode)

1. B22VE2
2. 2VB2E2
3. 2VE2B2
4. E22VB2

A galvanometer having a coil resistance of 60 shows full scale deflection when a current of 1.0 amp passes through it. It can be converted into an ammeter to read currents up to 5.0 amp by

1. putting in series a resistance of 15
2. putting in series a resistance of 240
3. putting in parallel a resistance of 15
4. putting in parallel a resistance of 240

The magnetic force acting on a charged particle of charge -2 C in a magnetic field of 2 T acting in y direction, when the particle velocity is (2 i + 3 j) 106 m s-1, is

1. 4 N in z direction
2. 8 N in y direction
3. 8 N in z direction
4. 8 N in -z direction

Under the influence of a uniform magnetic field, a charged particle moves with constant speed v in a circle of radius R. The time period of rotation of the particle

1. depends on R and not on v
2. is independent of both v and R
3. depends on both v and R
4. depends on v and not on R

A particle of mass m, charge Q and kinetic energy T enters a transverse uniform magnetic field of induction B. After 3 seconds the kinetic energy of the particle will be

1. T
2. 4 T
3. 3 T
4. 2 T

A closed loop PQRS carrying a current is placed in a uniform magnetic field. If the magnetic forces on segments PS, SR and RQ are F1, F2 and F3 respectively and are in the plane of the paper and along the directions shown, the force on the segment QP is [figure]

1. (F3 - F1)2 - F22
2. F3 - F1 + F2
3. F3 - F1 - F2
4. (F3 - F1)2 + F22