Draw a neat and labelled diagram of a D.C motor and explain its construction.   

Complete the diagram showing the path of $\alpha$, $\beta$ and $\gamma$ radiations in an electric field. 

Name the radiation which have the lowest penetrating power.

State energy change which occurs in:
Burning of coal.

A body when acted upon by a force of $10 \mathrm{kgf}$ gets displaced by $0.5 \mathrm{m}$. Calculate work done by the force when displacement is in direction of the force.

Name a machine which is used to multiply force.