Glossary
Electromagnetic Induction
The process of generating a voltage (and thus a current in a complete circuit) by changing a magnetic field.
Example:
Shaking a flashlight that uses a magnet moving through a coil to generate power for its light demonstrates this principle.
Electromotive Force (EMF)
The voltage or potential difference induced in a circuit due to a changing magnetic flux, driving an induced current.
Example:
The electromotive force generated in a car's alternator charges the battery.
Faraday's Law
States that the magnitude of the induced electromotive force (EMF) in a circuit is equal to the negative rate of change of magnetic flux through the circuit.
Example:
A generator uses Faraday's Law by rotating coils in a magnetic field to produce alternating current for homes.
Lenz's Law
States that the direction of the induced current or EMF is always such that it opposes the change in magnetic flux that produced it.
Example:
When you drop a strong magnet through a copper pipe, it falls slowly due to the opposing magnetic field generated by the induced currents, illustrating Lenz's Law.
Magnetic Flux (ΦB)
A measure of the total number of magnetic field lines passing through a given area, calculated as the integral of the magnetic field dotted with the area vector.
Example:
As a metal loop enters a region with a strong magnetic field, the magnetic flux through the loop increases, inducing a current.
Maxwell's Equations
A set of four fundamental equations that describe the behavior of electric and magnetic fields and their interactions with matter, forming the basis of classical electromagnetism.
Example:
The existence of electromagnetic waves, like light, is predicted directly from Maxwell's Equations.
Motional EMF
The electromotive force induced across a conductor as it moves through a uniform magnetic field.
Example:
A metal rod sliding on rails in a magnetic field will develop a motional EMF, causing current to flow if the circuit is closed.
Transformers
Devices that use electromagnetic induction to change (step up or step down) the voltage of an alternating current.
Example:
A laptop charger contains a transformer to reduce the wall outlet's high voltage to a safe level for the device.
Weber (Wb)
The SI unit for magnetic flux, equivalent to Tesla-meter squared (Tm²).
Example:
A large electromagnet might produce a magnetic flux of 0.5 Weber through a nearby coil.