In a certain region of space electric field E and magnetic field B are perpendicular ot each other and an electron enters region perpendicular to the direction of B and E both and moves undeflected, then velocity of electron is

Options

A. `(|overset(to)E|)/(|overset(to)B|)`
B. `overset(to) ( E ) xx overset(to)( B) `
C. `(|overset(to)B|)/(|overset(to)E|)`
D. `overset(to)( E ) .overset(to)( B )`

Answer

A

Explanation

For electron to pass undeflected,
Electric force on electron = magnetic force on electron
i.e., `eE = ev B`
or `v = ( E )/( B)`
or `v = (|overset(to)E|)/(|overset(to)B|)`