Physics: An Introduction Chapter 23 -- Reference Tools & Resources

Chapter 23: Magnetic Flux and Faraday's Law of Induction
Reference Tools & Resources

Reference Tools & Resources

I. Key Terms and Phrases

induced emf: a potential difference created by a changing magnetic flux.

magnetic flux: a measure of the extent to which a magnetic field "flows" through an area.

weber: the SI unit of magnetic flux equal to 1 T^.m².

Faraday's law of induction: the induced emf in a coil equals the rate of change of magnetic flux through the coil.

Lenz's law: the polarity of an induced emf is such that the induced current gives rise to a magnetic flux that opposes the original change in flux.

motional emf: the induced emf that results from the motion of a conductor through a magnetic field.

electric generator: a device designed to convert mechanical energy to electrical energy.

alternating current (AC): current that alternates in direction.

electric motor: a device designed to convert electrical energy into mechanical work.

self-induction: the creation of an induced emf in a coil due to its own changing current.

inductance: the proportionality constant between the induced emf in a coil and the rate of change in the current in that same coil.

henry: the SI unit of inductance.

inductor: a coil with a finite inductance used as a circuit element.

transformer: a device that uses induction to increase (step-up) or decrease (step-down) the voltage in a circuit.

II. Important Equations

Name/Topic Equation Explanation
magnetic flux F = BAcosq Magnetic flux measures the amount of magnetic field "flowing" through an area.

Faraday's law The induced emf from the rate of change in magnetic flux through a coil of N turns.

motional emf The magnitude of the induced emf from the motion of a conductor through a magnetic field.

electric generators E = NBAwsinwt The emf of an AC generator

inductance Faraday's law in terms of self-inductance.

RL circuits The time constant for an RL circuit.

stored energy The energy stored in the magnetic field of an inductor.

transformers The ratio of the potential differences in a transformer equals the ration of the turns.

Name/Topic	Equation	Explanation
magnetic flux	F = BAcosq	Magnetic flux measures the amount of magnetic field "flowing" through an area.
Faraday's law		The induced emf from the rate of change in magnetic flux through a coil of N turns.
motional emf		The magnitude of the induced emf from the motion of a conductor through a magnetic field.
electric generators	E = NBAwsinwt	The emf of an AC generator
inductance		Faraday's law in terms of self-inductance.
RL circuits		The time constant for an RL circuit.
stored energy		The energy stored in the magnetic field of an inductor.
transformers		The ratio of the potential differences in a transformer equals the ration of the turns.

III. Know Your Units

Quantity Dimension SI Unit
magnetic flux (F) [M][L²][A^-1][T^-2] Wb

inductance (L) [M][L²][T^-2][A^-2] H

Quantity	Dimension	SI Unit
magnetic flux (F)	[M][L²][A^-1][T^-2]	Wb
inductance (L)	[M][L²][T^-2][A^-2]	H