A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron:

A will turn towards right of direction of motion

B will turn towards left of direction of motion

C speed will decrease

D speed will increase

The answer is C.

Solution

Since the electron's velocity is along the direction of $\vec B$, the magnetic force ($q\vec v\times\vec B$) on it is zero. The electric force on the (negatively charged) electron, moving along the direction of $\vec E$, decelerates it, so its speed will decrease.

Concept Motion of a charge in parallel E and B fields

Motion in Combined Electric and Magnetic Fields in past papers

13 questions from this chapter have appeared across 10 exam years.

A uniform electric field and a uniform magnetic field are acting along the same direction in a certain region. If an electron is projected in the region such that its velocity is pointed along the direction of fields, then the electron:

Solution

Motion in Combined Electric and Magnetic Fields in past papers

Practice

Free resources

Platform

At the institute