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Q5 (NDA-I/2013) Science & Technology › Basic Science (Physics, Chemistry, Biology) › Electricity and magnetism Answer Verified

The motion of an electron in presence of a magnetic field is depicted in the figure given below. The force acting on the electron will be directed

Result
Your answer:  ·  Correct: B
Explanation

The direction of the magnetic force on a moving charged particle is determined by the Lorentz force law, expressed as F = q(v × B). According to the right-hand rule, for a positive charge, the force is perpendicular to both the velocity (v) and the magnetic field (B). However, since an electron carries a negative charge, the resulting force is directed opposite to the direction predicted for a positive charge. In the standard depiction where an electron moves in a plane with a magnetic field, applying the right-hand rule (fingers from v to B) would yield a direction into the page for a positive charge; thus, for the negatively charged electron, the force is directed out of the page. This force remains perpendicular to the motion, causing the electron to undergo circular or helical deflection without changing its speed.

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