An electron (mass 9 imes 10^{-31} kg and charge 1.6 imes 10^{-19} C) moving with speed c/100 (c = speed of light) is injected into a magnetic field \vec{B} of magnitude 9 imes 10^{-4} T perpendi

Question

An electron (mass 9 	imes 10^{-31} kg and charge 1.6 	imes 10^{-19} C) moving with speed c/100 (c = speed of light) is injected into a magnetic field \vec{B} of magnitude 9 	imes 10^{-4} T perpendicular to its direction of motion. We wish to apply a uniform electric field \vec{E} together with the magnetic field so that the electron does not deflect from its path. Then (speed of light c = 3 	imes 10^{8}\ \mathrm{m\,s^{-1}}):

Vishal Gupta · Accepted Answer

B. For no deflection the electric force must cancel the magnetic force: eE = evB, with \vec{E} perpendicular to both \vec{v} and \vec{B}. E = vB = 3	imes10^{6} 	imes 9	imes10^{-4} = 2.7	imes10^{3} = 27	imes10^{2} V/m.

Moving Charges and Magnetism

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