Moving Charges and Magnetism

A long straight wire of a circular cross-section with radius 'a' carries a steady current I. The current I is uniformly distributed across this cross-section. The plot of magnitude of magnetic field B with distance r from the centre of the wire is given by

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

A tightly wound long solenoid carries a current of 1.5 A. An electron is executing uniform circular motion inside the solenoid with a time period of 75 ns. The number of turns per metre in the solenoid is . [Take mass of electron me=9 10-31 kg, charge of electron |qe|=1.6 10-19 C, 0=4 10-7 NA2, 1 ns=10-9 s]

Consider a moving coil galvanometer (MCG): Choose the correct answer from the options given below:

1. A, D Only
2. A, B Only
3. A, B, E Only
4. B, D, E Only

A galvanometer having a coil of resistance 30 need 20 mA of current for full-scale deflection. If a maximum current of 3 A is to be measured using this galvanometer, the resistance of the shunt to be added to the galvanometer should be 30X , where X is

1. 447
2. 298
3. 149
4. 596

An electron projected perpendicular to a uniform magnetic field B moves in a circle. If Bohr's quantization is applicable, then the radius of the electronic orbit in the first excited state is :

1. h eB
2. 4h eB
3. h2 eB
4. 2h eB

A proton is moving undeflected in a region of crossed electric and magnetic fields at a constant speed of 2 105 m s-1. When the electric field is switched off, the proton moves along a circular path of radius 2 cm . The magnitude of electric field is x 104 N/C. The value of x is . Take the mass of the proton =1.6 10-27 kg.

Two long parallel wires X and Y, separated by a distance of 6 cm , carry currents of 5 A and 4A, respectively, in opposite directions as shown in the figure. Magnitude of the resultant magnetic field at point P at a distance of 4 cm from wire Y is x 10-5 T. The value of x is . Take permeability of free space as 0=4 10-7 SI units. [figure]