Moving Charges and Magnetism

A long straight wire of radius a carries a steady current I. The current is uniformly distributed across its cross section. The ratio of the magnetic field at a2 and 2a from axis of the wire is :

1. 4 : 1
2. 3 : 4
3. 1 : 1
4. 1 : 4

Match List I with List II Choose the correct answer from the options given below:

1. A-I, B-III, C-II, D-IV
2. A-IV, B-II, C-III, D-I
3. A-III, B-I, C-II, D-IV
4. A-IV, B-III, C-II, D-I

An element l = x i is placed at the origin and carries a large current I = 10 A. The magnetic field on the y-axis at a distance of 0.5 m from the element x of 1 cm length is: [figure]

1. 10 10-8 T
2. 8 10-8 T
3. 4 10-8 T
4. 12 10-8 T

Match List I with List II: Choose the correct answer from the options given below :

1. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
2. (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
3. (A)-(IV), (B)-(I), (C)-(III), (D)-(II)
4. (A)-(I), (B)-(III), (C)-(II), (D)-(IV)

In the given figure an ammeter A consists of a 240 coil connected in parallel to a 10 shunt. The reading of the ammeter is mA. [figure]

A coil having 100 turns, area of 5 10-3 m2, carrying current of 1 mA is placed in uniform magnetic field of 0.20 T such a way that plane of coil is perpendicular to the magnetic field. The work done in turning the coil through 90 is .

In a co-axial straight cable, the central conductor and the outer conductor carry equal currents in opposite directions. The magnetic field is zero :

1. inside the outer conductor
2. outside the cable
3. in between the two conductors
4. inside the inner conductor

A 2 A current carrying straight metal wire of resistance 1 , resistivity 2 10-6 , area of cross-section 10 mm2 and mass 500 g is suspended horizontally in mid air by applying a uniform magnetic field B. The magnitude of B is 10-1 T (given, g = 10 m/s2).

A galvanometer of resistance 100 when connected in series with 400 measures a voltage of upto 10 V. The value of resistance required to convert the galvanometer into ammeter to read upto 10 A is x 10-2 . The value of x is :

1. 2
2. 20
3. 800
4. 200

The electrostatic force ( F1 ) and magnetic force ( F2 ) acting on a charge q moving with velocity v can be written :

1. F1 = q B, F2 = q( B v)
2. F1 = q V E, F2 = q( B V)
3. F1 = q E, F2 = q( V B)
4. F1 = q E, F2 = q( B V)