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

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 circular coil of wire of radius 'r' has 'n' turns and carries a current 'I'. The magnetic induction (B) at a point on the axis of the coil at a distance $\sqrt{3}r$ from its center is :

1.  $\frac{{\mathrm{\mu }}_0\mathrm{In}}{4\mathrm{r}}$

2.  $\frac{{\mathrm{\mu }}_0\mathrm{In}}{8\mathrm{r}}$

3.  $\frac{{\mathrm{\mu }}_0\mathrm{In}}{16\mathrm{r}}$

4.  $\frac{{\mathrm{\mu }}_0\mathrm{In}}{32\mathrm{r}}$

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?

The unit of reduction factor of the tangent galvanometer is 

1. Ampere

2. Gauss

3. Radian

4. None of these