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Unit 4 · Magnetism & Electromagnetism Flashcards Cheat Sheet Essentials Visual Review MC Practice FRQ Practice

AP Physics 2 Unit 4 Visual Review

A topic-by-topic visual walkthrough of Unit 4: Magnetism & Electromagnetism — magnetic fields, forces on moving charges and wires, and electromagnetic induction.

← Back to Unit 4 hub
TOPIC 4.1 Magnetic Fields N S field lines exit N, enter S Key facts about B fields Magnetic field B is a VECTOR, measured in teslas (T). Field lines run N → S outside the magnet, forming closed loops (no monopoles). Like poles repel; opposite poles attract. Magnetism comes from MOVING charges (electron spin & currents). Cutting a magnet in half makes two magnets. B is a vector (teslas); lines run N → S in closed loops; no magnetic monopoles. The Review Hub · AP Physics 2 · Unit 4 TOPIC 4.2 Magnetism & Moving Charges Force on a moving charge F = q v B sin θ Maximum when v ⊥ B (θ = 90°); ZERO when v ∥ B. The force is ALWAYS perpendicular to v, so it does NO work — only turns the path. v F B into page → charge moves in a circle Circular motion & the right-hand rule A charge in a uniform B moves in a circle: qvB = mv²/r → r = mv/(qB). Use the right-hand rule for direction. F = qvB sin θ ⊥ to v → does no work; charge circles with r = mv/(qB). The Review Hub · AP Physics 2 · Unit 4 TOPIC 4.3 Magnetism & Current-Carrying Wires A current makes a field B = μ₀ I / (2π r) A long straight wire makes circular field loops around it (right-hand rule: thumb along I, fingers curl along B). μ₀ = 4π×10⁻⁷ T·m/A; B weakens with distance r. I B loops circle the wire Parallel wires exert forces Two wires with currents in the SAME direction attract; OPPOSITE currents repel. Force on a wire: F = BIL sin θ. A wire makes B = μ₀I/2πr; force on a wire F = BIL sin θ. The Review Hub · AP Physics 2 · Unit 4 TOPIC 4.4 Electromagnetic Induction & Faraday's Law EMF = −N ΔΦ / Δt Φ = B A cos θ a CHANGING magnetic flux induces a voltage What changes the flux? Change B, the loop area A, or the angle θ. Move a magnet toward/away from a coil, or rotate the coil (this is a generator). Faster change → bigger induced EMF. Static field → no EMF; it must CHANGE. Lenz's law (the minus sign) The induced current OPPOSES the change in flux that created it. Push a N pole in → coil face becomes N to repel it (energy conservation). Basis of generators, transformers & motors. Changing flux induces EMF = −NΔΦ/Δt; induced current opposes the change (Lenz). The Review Hub · AP Physics 2 · Unit 4
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How to use the visual review

Spend 30 seconds per slide before clicking next. Look at the diagram, then ask yourself: "Could I draw this from memory and explain it?"

Use the fullscreen button () on desktop for the best experience. Use arrow keys to navigate. Tap "Show all slides" to jump around.

This is great for review the night before the exam — fast, visual, and covers everything you need to remember about Unit 4's magnetism and electromagnetism.