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Asked in GSEB Board July 2022 · Lorentz force and work done
Idea: a charge q sitting in an electric field ⃗E and a magnetic field ⃗B feels two forces at once, and the Lorentz force is their sum.
Electric part: q⃗E — along the field for a positive charge, and present whether the charge moves or not.
Magnetic part: q(⃗v×⃗B) — it needs motion, it is perpendicular to both ⃗v and ⃗B, and its magnitude is qvB sin θ.
Adding them: ⃗F=q[⃗E+(⃗v×⃗B)].
The order inside the cross product matters: ⃗B×⃗v would point the opposite way.
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