Key Concepts of Faraday's Law of Induction to Know in AP Physics C: E&M (2025)

Electromagnetic Induction

"The process of using shifting magnetic fields to generate electric current. This phenomenon is explained by Faraday's Law, which states that the rate at which magnetic flux changes via a circuit determines the induced electromotive force (emf)."

Faraday's Law

"A principle that explains how an electric current generated by a conductor is related to a changing magnetic field. It asserts that the rate at which magnetic flux changes through a conductor is equal to the induced electromotive force (emf) in that conductor."

Lenz's Law

"A principle that establishes the direction of the induced current. It states that the induced EMF will always oppose the change in magnetic flux that caused it, ensuring conservation of energy."

Magnetic Flux

"The amount of magnetic field passing through a specific area, typically calculated as the dot product of the magnetic field vector and the area vector. Measured in Weber (Wb)."

Electromotive Force (EMF)

"The voltage induced in a conductor due to the changing magnetic flux. This can be caused by moving through a magnetic field, a changing magnetic field, or deforming the circuit."

Induced EMF

"The electromotive force created when a circuit's magnetic flux changes, which can be due to motion through a magnetic field, a changing magnetic field, or deformation of the circuit."

Induced Current

"The flow of charge resulting from the induced EMF in a conductor, typically caused by a changing magnetic field."

Conservation of Energy

"A fundamental principle stating that energy cannot be created or destroyed, only transformed. This underpins Lenz's Law, preventing infinite energy generation."

Faraday's Law Formula

"E = -dΦB/dt, where E is the induced EMF, ΦB is the magnetic flux, and dΦB/dt is the rate of change of magnetic flux."

Lenz's Law Formula

"Emf = -N * (ΔΦ/Δt), where Emf is the induced voltage, N is the number of loops, ΔΦ is the change in magnetic flux, and Δt is the change in time."

Electric Generators

"Devices that use electromagnetic induction to convert mechanical energy into electrical energy. A coil rotating in a magnetic field induces an EMF, creating an electric current."

Transformers

"Devices that transfer electrical energy between circuits using electromagnetic induction. A changing current in the primary coil induces an EMF in the secondary coil."

Induction Cooktops

"Devices that use electromagnetic induction to heat cookware. A changing magnetic field causes electric currents to flow in the metal cookware, which heats up due to electrical resistance."

Magnetic Field

"A field produced by moving charges or magnetic materials, affecting other charges and magnetic materials in the area."

Increasing Magnetic Field

"According to Faraday's Law, an induced EMF occurs when the magnetic field through a coil increases, and Lenz's Law states that the induced current opposes this increase."

Decreasing Magnetic Field

"When the magnetic field decreases, the induced EMF creates a current that opposes the decrease, according to Faraday's and Lenz's Laws."