EE422 Magnetism and Electromagnetic Induction Part 2

Magnetic Circuit

A closed path in which magnetic induction or flux flows, established upon the application of magnetomotive force (mmf).

Magnetomotive Force

A force that sets up or tends to set up magnetic flux in a magnetic circuit, calculated as mmf = NI.

Reluctance

Property of material that opposes flux flow, equal to the ratio of mmf in a magnetic circuit to the magnetic flux through any cross section.

Permeance

The reciprocal of reluctance, indicating the ease with which magnetic flux is developed.

Flux

Indicates the apparent stress in the space surrounding an energized coil or magnet.

Faraday's Law

The law of Electromagnetic Induction stating that an electrical field is induced in any system where the magnetic field is changing with time.

Induced EMF

The voltage generated by a conductor or coil moving in a magnetic field, opposing the cause that produces it.

Inductance

A property of an electric circuit where emf is induced due to changing magnetic flux, typically found in conducting coils.

Self Inductance

The property of a coil opposing the change of current flowing through itself, expressed in Henry/Henries.

Mutual Inductance

The property of one coil opposing the change of current in another neighboring coil, with a coefficient of coupling between them.

Coupling

The measure of the extent to which two coils in a network are magnetically linked or share magnetic flux.

Mutual inductance

The property of a circuit where a change in current in one coil induces a voltage in another coil, measured in henries (H).

Inductance

The property of a circuit component (like a coil) that opposes any change in current, measured in henries (H).

Flux linkages

The product of the magnetic flux and the number of turns in a coil, measured in weber-turns (Wb-turns).

Energy stored

The amount of energy stored in a system, in this context, the energy stored in the magnetic field of the coils, measured in joules (J).

First Law of Electromagnetic Induction

This law states that “Whenever a conductor cuts across the magnetic field, an emf is induced in the conductor.” or “Whenever the magnetic flux linking with any circuit (or coil) changes, an emf is induced in the circuit.”

Second Law of Electromagnetic Induction

This law states that “The magnitude of induced emf in a coil is directly proportional to the rate of change of flux linkages.

Dynamically Induced EMF

By either moving the conductor and keeping the magnetic field system stationary or moving the magnetic field system and keeping the conductor stationary, in such a way that conductor cuts across the magnetic field (as in case of DC and AC generators). The emf induced in this way ______

Statically Induced EMF

By changing the flux linking with the coil (or conductor) without moving either coil or field system. However, the change of flux produced by the field system linking with the coil is obtained by changing the current in the field system (solenoid), as in transformers. The emf induced in this way ______

Series Aiding

sources of electromotive force (emf) which give the ability to the current to flow in the same direction. Additive fields

Series opposing

sources of electromotive force (emf) which give the ability to the current to flow in opposite direction. Subtractive fields

Parallel aiding

When the fields (or mmfs.) produced by them are in the same direction

Parallel opposing

When the fields (or mmfs.) produced by them are in the opposite direction