I keep getting “Biot-Savart law” questions wrong in Moving Charges & Magnetism. What's the trap?
treating magnetic-field contributions as scalars without direction.
The usual trap: treating magnetic-field contributions as scalars without direction. How to avoid it: right-hand direction before integration. Go back to the definition — Each current element contributes a magnetic field perpendicular to its direction and the line to the observation point. Integrating these vector contributions gives the field of the whole conductor.
Key point
Biot-Savart law
Common mistake
treating magnetic-field contributions as scalars without direction.
Memory tip
right-hand direction before integration.
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