Question

A uniform magnetic field exists in the plane of paper pointing from left to right as shown in the figure. In the field, an electron and a proton move as shown. The electron and the proton experience?

• A. Forces both pointing into the plane of the paper.
• B. Forces both pointing out of the plane of the paper.
• C. Force pointing into the plane of the paper and out of the plane of the paper, respectively.
• D. Force pointing opposite and along the direction of the uniform magnetic field respectively.

Answer 1

The correct option is A Forces both pointing into the plane of the paper.

The direction of force exerted on both the charges can be determined using fleming's left hand rule. The forefinger points to the direction of the magnetic field. The middle finger points in the direction of the current. The thumb gives the direction of force or motion acting on the conductor.

However, the charge on the electron is opposite to the proton so in a way the direction of the conventional current is same for both the electron and the proton. Hence, the force experienced by both the charges will be into the plane of the paper.

Hence, option A is the correct answer.