question_answer

A uniform electric field and a uniform magnetic field are produced, pointed in the same direction. An electron is projected with its velocity pointing in the same direction [NCERT 1980; CBSE PMT 1993; JIPMER 1997;  AIEEE 2005]

A)            The electron will turn to its right

B)            The electron will turn to its left

C)            The electron velocity will increase in magnitude

D)            The electron velocity will decrease in magnitude

Correct Answer: D

Solution :

                   Since electron is moving is parallel to the magnetic field, hence magnetic force on it \[{{F}_{m}}=0\]. The only force acting on the electron is electric force which reduces it?s speed.