Q. A uniform electric field and a uniform magnetic field exist in a region in the same direction. An electron is projected with a velocity pointed in the same direction. Then the electron will
A) Be deflected to the left without increase in speed
B) Be deflected to the right without increase in speed
C) Not be deflected but its speed will decrease
D) Not be deflected but its speed will increase
Explanation
(c) Magnetic force on electron $= Bev\sin\theta$
$= Bev\sin 0 = \ $zero
Electron will not be deflected due to magnetic field. Electric force on electron $= Ee$
This force is opposite to direction of motion of the electron. The speed of electron will decrease. Hence the electron will not be deflected but its speed is decreased
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.