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A point charge moves with velocity v in a region having both an electric field E and a magnetic field B. The total Lorentz force on the charge q is best written as:
AF = q(E + v × B)
BF = q(E − v × B)
CF = q(B + v × E)
DF = q(v × E + B)
Answer & Solution
Correct answer: A. F = q(E + v × B)
1. The Lorentz force combines the electric force and the magnetic force on a charge.
2. Electric part: $\mathbf{F}_E = q\mathbf{E}$.
3. Magnetic part: $\mathbf{F}_B = q(\mathbf{v} \times \mathbf{B})$.
4. Adding them: $\mathbf{F} = q[\mathbf{E} + \mathbf{v} \times \mathbf{B}]$.
_Source: NCERT Class 12 Physics Ch 4 "Moving Charges and Magnetism", p.134_
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