An electron is projected with velocity $v_0$ in a uniform electric field $E$ perpendicular to the field. Again it is projected with velocity $v_0$ perpendicular to a uniform magnetic filed $B$. If $r_1$ is initial radius of curvature just after entering in the electric and $r_2$ is initial radius of curvature just after entering in magnetic field then the ratio $\frac{r_1}{r_2}$ is equal to

A mass spectrometer is a device which select particle of equal mass. An iron with electric charges $q>0$ starts at rest from a source $S$ and is accelerated through a potential difference $V$. It passes through a hole into a region of constant magnetic field $\overrightarrow{B}$ perpendicular to the plane of the paper as shown in the figure. The particle is deflected by the magnetic field and emerges through the bottom hole at a distance $d$ form the top hole. The mass of the particle is

A block of mass $m$ and charge $q$ is released on a long smooth inclined plane magnetic field $B$ is constant, uniform, horizontal and parallel to surface as shown. Find the time from start when block loses contact with the surface

In the figure shown a current $I_1$ is established in the long straight wire $AB$. Another wire $CD$ carrying current $I_2$ is placed in the plane of the paper. The line joining the ends of this wire is perpendicular the wire $AB$. The force on the wire $CD$ is

A dis magnet has its poles on its opposing flat surfaces. An insulated copper wire placed on the dis magnet as shown in the diagram

The insulated wire was connected to a $DC$ battery, the wire was observed to move in the direction of the arrow.

Which statement describes the direction of the magnetic field and the direction to the current.

A single circular loop of radius $1.00 \mathrm{m}$ carries a current of $10.0 \mathrm{mA}$. It is placed in a uniform magnetic field of magnitude $0.500 \mathrm{T}$ that is directed parallel to the plane of the loop as suggested in the figure. The magnitude of the torque exerted on the loop by the magnetic field is.