Induced Voltages and Inductance (Chapter 20)

Vocabulary-style flashcards covering the principles of induced voltages, magnetic flux, Faraday's and Lenz's laws, motional emf, generators, and self-inductance based on Chapter 20 of Foundation Physics 2.

Magnetic flux ($\Phi_B$)

A measure of the number of magnetic field lines that cross a given area, defined as $\Phi_B = BA\cos(\theta)$ where $\theta$ is the angle between the magnetic field and the normal to the plane of the loop.

Weber ($Wb$)

The SI unit of magnetic flux, where $1\,Wb = 1\,Tm^2$.

Faraday’s Law of Induction

The law stating that the instantaneous emf induced in a circuit equals the negative of the rate of change of magnetic flux with respect to time through the circuit, given by $\varepsilon = -N \frac{\Delta \Phi_B}{\Delta t}$.

Induced current

An electrical current produced in a circuit by a changing magnetic field or motion relative to a magnet, even when no battery is present in that circuit.

Lenz’s Law

A law stating that an induced current travels in a direction that creates a magnetic field with flux opposing the change in the original flux through the circuit.

Ground Fault Interrupter (GFI)

A safety device that protects against electrical shock, serving as an application of Faraday's Law.

Motional emf

The potential difference maintained across a conductor of length $l$ moving with velocity $v$ through a uniform magnetic field $B$, calculated as $\Delta V = Blv$.

Alternating Current (AC) Generator

A device that converts mechanical energy to electrical energy using a wire loop rotating in a magnetic field, producing an emf given by $\varepsilon = NBA\omega\sin(\omega t)$, and connected to an external circuit via slip rings.

Direct Current (DC) Generator

A generator that uses a split ring or commutator to ensure the output voltage always has the same polarity, resulting in a pulsating current.

Back emf

An induced emf in a motor that tends to reduce the applied current as the coil begins to rotate.

Self-inductance

A phenomenon where a changing current in a circuit induces an emf that opposes that change, with the proportionality constant $L$ defined as $L = N \frac{\Delta \Phi_B}{\Delta I}$.

Henry ($H$)

The SI unit of inductance, where $1\,H = 1\,Vs/A$.

Inductor

A circuit element specifically designed to have a large inductance, acting as a measure of opposition to the rate of change in the current.

Time constant ($\tau$)

The time required for the current in an RL circuit to reach $63.2\%$ of its final value $\varepsilon / R$, defined as $\tau = \frac{L}{R}$.

Energy stored by an inductor ($PE_L$)

The energy stored in the magnetic field of an inductor while a battery does work to produce a current, calculated as $PE_L = \frac{1}{2} LI^2$.