Question

A proton enters a uniform magnetic field with a path perpendicular to the field lines and moves in a circular path of radius $R$. An electron enters the same magnetic field at the same speed in a path perpendicular to the field.
Compared to the protons path, the radius of the electrons circular path is:

• A. The same radius.
• B. A larger radius.
• C. A smaller radius.
• D. The electron moves in a straight line.

Answer 1

The correct option is C A smaller radius.

$m{v}^2/R=Bqv$( centripetal force= force of magnetic field)

or $R=\frac{mv}{Bq}$

A proton enters a uniform magnetic field with a path perpendicular to the field lines and moves in a circular path of radius R. An electron enters the same magnetic field at the same speed in a path perpendicular to the field.

Compared to the protons path, the radius of the electrons circular path is A smaller radius. since the mass of electron is less.