A circular loop of radius $9.7 \mathrm{cm}$ carries a current $2.3 \mathrm{A}$. Obtain the magnitude of the magnetic field at a distance of 9.7 cm from the centre of the loop but on the axis. 

In a cyclotron protons are to be accelerated. Radius of its D is $60 \mathrm{cm}$. and its oscillator frequency is $10 \mathrm{MHz}$. What will be the kinetic energy of the proton thus accelerated? 

Proton mass $=1.67\times {10}^{-27}\mathrm{kg}$ $\left.\mathrm{e}=1.60\times {10}^{-19}\mathrm{C},1\mathrm{eV}=1.6\times {10}^{-19}\mathrm{J}\right)$

A wire loop of the form shown in the figure carries a current I. Obtain the magnitude and direction of the magnetic field at P. Given: $\mathrm{B}=\frac{{\mathrm{\mu }}_0\mathrm{I}}{4\mathrm{\pi R}}\sqrt{2}$