Write the expression for magnetic potential energy of a magnetic dipole kept in a uniform magnetic field and explain the terms.

In a region, an electric field $\overrightarrow{E}=5x^3 \hat{j} {\mathrm{NC}}^{-1}$ and a magnetic field of $\overrightarrow{B}=0.1 \hat{k} \mathrm{T}$ are applied. A beam of positively charged particles is projected along X-direction. Find the velocity of particles that move undeflected in these crossed fields.

Give the principle of a cyclotron and draw the neat labelled schematic diagram of a cyclotron.

Obtain the expression for the force between the two conductors carrying current. Hence, define "ampere".