A current-carrying closed Loop in the form of a right isosceles triangle ABC is placed in xy plane in a uniform magnetic field acting along the y-axis as shown in the figure. If the magnetic force on the arm AC is $\overrightarrow{F}$, then force on the arm BC and AB are respectively

1. zero, zero

2. $-\overrightarrow{F}<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>zero$

3. $\overrightarrow{F}<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>-\overrightarrow{F}$

4. $\overrightarrow{F}<mspace\; width="1em"></mspace>and<mspace\; width="1em"></mspace>zero$

A uniform electric field and a uniform magnetic field are acting in the same direction in a certain region. If a proton is projected in this region such that its velocity is pointed along the direction of fields, then the proton :

1.  will turn towards the left of the direction of motion

2.  will turn towards the right of the direction of motion

3.  will speed up

4.  will slow down

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

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.  $\frac{2\mathrm{qB}\left(\mathrm{b}<mspace\; width="1em"></mspace>-<mspace\; width="1em"></mspace>\mathrm{a}\right)}{\mathrm{m}}<mspace\; width="1em"></mspace>$

2.  $\frac{\mathrm{qB}\left(\mathrm{b}<mspace\; width="1em"></mspace>+<mspace\; width="1em"></mspace>\mathrm{a}\right)}{2\mathrm{m}}<mspace\; width="1em"></mspace>$

3.  $\frac{\mathrm{qB}\left(\mathrm{b}<mspace\; width="1em"></mspace>-<mspace\; width="1em"></mspace>\mathrm{a}\right)}{\mathrm{m}}<mspace\; width="1em"></mspace>$

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