Magnetic force quiz for AP Physics 2: 10 questions with answers

Quick answer: A moving charge or a current produces a magnetic field, and a magnetic field pushes sideways on other moving charges. This AP Physics 2 quiz checks magnetic force with 10 multiple-choice questions and instant feedback; every answer comes with a short explanation.

Ten questions with one correct option each. The distractors come from real mistakes, such as pushing a charge along the field lines. Read the short explanation after each question to see which step catches you out.

Level: AP Physics 2 (algebra-based) · Curriculum: AP P2 Unit 12

What happens to the magnetic field of a long wire when the distance from it is doubled?

What is the angle between the magnetic force on a moving charge and the velocity?

A charged particle moves parallel to a uniform magnetic field. What force acts on it?

A proton moves in a circle in a uniform field. What happens to the radius if the speed doubles?

What provides the centripetal force on a charge moving in a circle in a magnetic field?

Which expression gives the force on a straight wire of length L in a field B?

Two parallel wires carry currents in the same direction. What do they do?

What is 1 tesla equal to?

An electron and a proton enter the same field at the same speed. Which has the larger radius?

At the midpoint between two parallel wires carrying equal currents in the same direction, what is the field?

Field of a long straight wire — B = μ₀I/(2πr)

Value of μ₀ — 4π × 10⁻⁷ T·m/A

Magnetic force on a moving charge — F = |q|vB sin θ

Radius of circular path in a field — r = mv/(qB)

Force on a straight wire — F = BIL sin θ

Unit of magnetic field — tesla, 1 T = 1 N/(A·m)

Work done by magnetic force — Zero: force is perpendicular to velocity.

Parallel currents — Attract; opposite currents repel.

Force per metre between wires — F/L = μ₀I₁I₂/(2πd)

Velocity selector condition — qE = qvB, so v = E/B