When an electron enters perpendicularly in a magnetic field with velocity v, time period of its revolution is T. If it enters in the same magnetic field with a velocity 2v, then its time period will be:

1.  2T

2.  4T

3.  $\frac{\mathrm{T}}{2}$

4.   T

A positively charged particle descends vertically. In which direction will the horizontal component of the earth's magnetic field deflect?

1. east

2. west

3. north

4. south

What is the magnetic dipole moment of the given loop?

The magnetic field at center due to the orbital motion of the electron in the hydrogen atom is :

1.  12.5 tesla

2.  5 tesla

3.  24 tesla

4.  1 tesla

The figure shows a particle of charge q and mass m moving with velocity v along the x-axis enters a region of the uniform magnetic field. The minimum value of v so that the charge q is deflected by an angle $30°$ is

1.  $\frac{2\mathrm{qB}\left(\mathrm{b} - \mathrm{a}\right)}{\mathrm{m}}$

2.  $\frac{\mathrm{qB}\left(\mathrm{b} + \mathrm{a}\right)}{2\mathrm{m}}$

3.  $\frac{\mathrm{qB}\left(\mathrm{b} - \mathrm{a}\right)}{\mathrm{m}}$

4.  $\frac{\mathrm{qBb}}{2\mathrm{m}}$

An electron is traveling along the x-direction. It encounters a magnetic field in the y-direction. Its subsequent motion will be:

1.  Straight-line along the x-direction

2.  A circle in the xz-plane

3.  A circle in the yz-plane

4.  A circle in the xy-plane

A closed-loop (of any shape) carrying current lies in the x-y plane. What happens when a uniform magnetic field B is present in the region such that the loop experiences zero force?

A galvanometer of resistance 240 Ω allows only 4% of the main current after connecting a shunt resistance. What is the value of shunt resistance?

1.  10 $\mathrm{\Omega }$

2.  20 $\mathrm{\Omega }$

3.  8 $\mathrm{\Omega }$

4.  5 $\mathrm{\Omega }$

The dots in the figure depict a magnetic field that is perpendicular to the plane of the paper and emanates from it. The trajectory of a particle in the plane of the paper is depicted by the curve ABC. What exactly is the particle?

A long solenoid has 800 turns per meter length of the solenoid. A current of 1.6 A flows through it. The magnetic induction at the end of the solenoid on its axis is:

1.  $16\times {10}^{-4} \mathrm{T}$

2.  $8\times {10}^{-4} \mathrm{T}$

3.  $32\times {10}^{-4} \mathrm{T}$

4.  $4\times {10}^{-4} \mathrm{T}$