Question

A uniform electric field and a uniform magnetic field are produced in the same direction. An electron is projected with its velocity in the same direction, then the

• A. electron will turn to its right
• B. electron will turn to its left.
• C. electron velocity will increase in magnitude.
• D. electron velocity will decrease in magnitude.

Answer 1

The correct option is D electron velocity will decrease in magnitude.

These will a force of magnitude qE on electron in the opposite direction of electric field. So, velocity will decrease in magnitude of electron. Now since velocity direction and magnetic field direction is same, there will not be any force due to magnetic force.
Since $F=q(\overrightarrow{V}\times \overrightarrow{B})$
$=qVBsin{0}^0$
$=0$ $(\because sin{0}^0=0)$