Moving Charges and Magnetism

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)

A solenoid of length 0.5 m has a radius of 1 cm and is made up of 'm' number of turns. It carries a current of 5 A. If the magnitude of the magnetic field inside the solenoid is 6.28 10-3 T then the value of m is .

An electron is projected with uniform velocity along the axis inside a current carrying long solenoid. Then :

1. the electron will experience a force at 45 to the axis and execute a helical path.
2. the electron will be accelerated along the axis.
3. the electron path will be circular about the axis.
4. the electron will continue to move with uniform velocity along the axis of the solenoid.

The magnetic field existing in a region is given by B=0.2(1+2x) k. A square loop of edge 50 cm carrying 0.5 A current is placed in x-y plane with its edges parallel to the x-y axes, as shown in figure. The magnitude of the net magnetic force experienced by the loop is mN. [figure]

Two parallel long current carrying wires separated by a distance 2r are shown in the figure. The ratio of magnetic field at A to the magnetic field produced at C is x7. The value of x is . [figure]

A galvanometer has a resistance of 50 and it allows maximum current of 5 mA. It can be converted into voltmeter to measure up to 100 V by connecting in series a resistor of resistance :

1. 19500
2. 5975
3. 20050
4. 19950