Magnetism and Electromagnetism practice quiz

Key ideaField lines leave north poles and enter south poles, and they form closed loops. A compass needle points along the field.

Common mistakeThinking field lines start or stop like electric field lines do.

Key ideaF = qvB sin θ, perpendicular to both v and B (right-hand rule). The force changes the direction of motion but not the speed.

Common mistakeForgetting to reverse the direction for a negative charge, or saying the force does work.

Key ideaA long wire’s field circles it, B = μ₀I/2πr. Parallel currents attract.

Common mistakePointing the field radially instead of around the wire.

Key ideaAn emf is induced only when the magnetic flux changes, and the induced current opposes that change (Lenz’s law).

Common mistakeThinking a strong but constant field induces a current.