Moving Charges and Magnetism

A moving coil galvanometer of resistance 100 shows a full scale deflection for a current of 1 mA. The value of resistance required to convert this galvanometer into an ammeter, showing full scale deflection for a current of 5 mA, is

1. 25
2. 2.5
3. 0.5
4. 10

Two identical circular loops P and Q each of radius r are lying in parallel planes such that they have common axis. The currents through P and Q are I and 4I respectively in clockwise direction as seen from O. The net magnetic field at O is : [figure]

1. 0 I4 2r towards Q
2. 3 0 I4 2r towards Q
3. 3 0 I4 2r towards P
4. 0 I4 2r towards P

The current passing through a conducting loop in the form of equilateral triangle of side 4 3 cm is 2 A. The magnetic field at its centroid is 10-5 T. The value of is . (Given: 0 = 4 10-7 SI units)

1. 3 3
2. 2 3
3. 3
4. 32

A current carrying solenoid is placed vertically and a particle of mass m with charge Q is released from rest. The particle moves along the axis of solenoid. If g is acceleration due to gravity then the acceleration (a) of the charged particle will satisfy :

1. a > g
2. a = 0
3. 0 < a < g
4. a = g

An infinitely long straight wire carrying current I is bent in a planar shape as shown in the diagram. The radius of the circular part is r. The magnetic field at the centre O of the circular loop is : [figure]

1. - 02 Ir( + 1) i
2. - 02 Ir( - 1) i
3. 02 Ir( + 1) i
4. 02 Ir( - 1) i

Figure shows a current carrying square loop ABCD of edge length 'a' lying in a plane. If the resistance of the ABC part is r and that of ADC part is 2r, then the magnitude of the resultant magnetic field at centre of the square loop is [figure]

1. 2 0 I3 a
2. 2 0 I3 a
3. 3 0 I 2a
4. 0 I2 a

A particle of charge q, mass m and kinetic energy E enters a magnetic field perpendicular to its velocity and undergoes a circular arc of radius (r). Which of the following curves represents the variation of r with E?

1. [figure]
2. [figure]
3. [figure]
4. [figure]

Uniform magnetic fields of different strengths (B1 and B2), both normal to the plane of the paper exist as shown in the figure. A charged particle of mass m and charge q, at the interface at an instant, moves into the region 2 with velocity v and returns to the interface. It continues to move into region 1 and finally reaches the interface. What is the displacement of the particle during this movement along the interface? [figure] (Consider the velocity of the particle to be normal to the magnetic field and B2 > B1)

1. mvqB1 (1 - B1B2 ) 2
2. mvqB1 (1 - B2B1 ) 2
3. mvqB1 (1 - B2B1 )
4. mvqB1 (1 - B1B2 )

A particle of charge 1.6 and mass 16 is present in a strong magnetic field of 6.28 T. The particle is then fired perpendicular to magnetic field. The time required for the particle to return to original location for the first time is s (rounded off to the nearest integer). ( = 3.14)

A loop ABCDA, carrying current I = 12 A, is placed in a plane, consists of two semi-circular segments of radius R1 = 6 m and R2 = 4 m. The magnitude of the resultant magnetic field at center O is k 10-7 T. The value of k is . (Given 0 = 4 10-7 T m A-1) [figure]