Question

A particle of charge q and velocity v passes undeflected though a space with non-zero electric field E and magnetic field B. The undeflecting conditions will hold if

• A. signs of both q and E are reversed
• B. signs of both q and B are reversed
• C. both B and E are doubled in magnitude
• D. v=E/B

Answer 1

The correct option is C

both B and E are doubled in magnitude

$\overrightarrow{F_e}=qeB\hat{n}\overrightarrow{F_e}=qvB\widehat{(-n)}$

Thus it both E and B are doubled the above conditions are not affected.