Moving Charges And Magnetism

In a cathode ray tube, a potential difference of 3000 volts is maintained between the deflector plates whose separation is \(2 \mathrm{~cm}\). A magnetic field of \(2.5 \times 10^{-3} \mathrm{~Wb} / \mathrm{m}^2\) at right angles to electric field gives no deflection of the electron beam, which received an initial acceleration by a potential difference of \(10000 \mathrm{~V}\). Calculate \((\mathrm{e} / \mathrm{m})\) of an electron.