Moving Charges and Magnetism · Question 54

A current loop consists of two identical semicircular parts each of radius R, one lying in the x-y plane and the other in x-z plane. If the current in the loop is i. The resultant magnetic field due to the two semicircular parts at their common centre is

1. 0 i2 2R
2. 0 i2R
3. 0 i4R
4. 0 i 2R

A closely wound solenoid of 2000 turns and area of cross-section 1.5 10-4 m2 carries a current of 2.0 A. It is suspended through its centre and perpendicular to its length, allowing it to turn in a horizontal plane in a uniform magnetic field 5 10-2 tesla making an angle of 30 with the axis of the solenoid. The torque on the solenoid will be

1. 3 10-3 N m
2. 1.5 10-3 N m
3. 1.5 10-2 N m
4. 3 10-2 N m

A particle having a mass of 10-2 kg carries a charge of 5 10-8 C. The particle is given an initial horizontal velocity of 105 m s-1 in the presence of electric field E and magnetic field B. To keep the particle moving in a horizontal direction, it is necessary that Which one of the following pairs of statements is possible ?

1. A and C only
2. C and D only
3. B and C only
4. B and D only

Two identical bar magnets are fixed with their centers at a distance d apart. A stationary charge Q is placed at P in between the gap of the two magnets at a distance D from the centre O as shown in the figure [figure] The force on the charge Q is

1. zero
2. directed along OP
3. directed along PO
4. directed perpendicular to the plane of paper

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