Principles of Electrodynamics and Generators

Practice flashcards covering the fundamental concepts of electromagnetic induction, AC and DC generators, and Faraday's Law as presented in the lecture notes.

Electromagnetic induction

The phenomenon where an altered magnetic field induces an emf and therefore letting a current flow in a conductor.

Fleming's right hand-dynamo rule

A rule used to determine the direction of induced current: the index finger points in the direction of the magnetic field ($B$), the thumb in the direction of motion or force ($F$), and the middle finger shows the direction of induced current ($I$).

Induced emf

The potential difference caused by a changing magnetic field as a conductor is forced through that magnetic field.

Magnetic flux ($\Phi$)

The amount of magnetic field lines that go through a determined surface, calculated as $\Phi = BA \cos(\theta)$.

Magnetic flux density ($B$)

Also known as the magnetic field, it is the amount of field lines per square meter of the surface it moves through, measured in tesla ($T$).

Tesla ($T$)

The unit of magnetic flux density, defined as $1\,T = 1\,Wb \cdot m^{-2}$.

Faraday's Law

The magnitude of the emf ($\epsilon$) induced in a coil is directly proportional to the rate of change of the magnetic flux ($\epsilon = -N \frac{\Delta \Phi}{\Delta t}$).

Weber ($Wb$)

The unit for magnetic flux ($\Phi$), also equivalent to tesla-meter ($T \cdot m^2$).

Generator (dynamo)

A device that converts mechanical energy into electrical energy using the principle of electromagnetic induction.

Alternating current generator (AC-generator)

A generator that causes a coil to rotate mechanically in a uniform magnetic field to produce alternating current.

Slip rings

Components in an AC-generator (traditionally labeled $S_1$ and $S_2$) that ensure the current in the external circuit is the same as the circuit in the coil.

Brushes

Carbon or copper blocks (labeled $B_1$ and $B_2$) that stay stationary and press against the rotating rings to divert the induced current to the external circuit.

Alternating current cycle

One complete change in the direction of the current during one revolution of the coil (or anchor) in a generator.

Direct current generator (DC-generator)

A generator designed to deliver direct current to the external circuit by using a split-ring commutator.

Split-ring commutator

A metal ring divided into two halves with a gap between them that ensures the current in the brushes and external circuit always flows in the same direction.

Bicycle dynamo

A device where a magnet fixed to an anchor rotates near a coil to provide electricity for a headlight via changed magnetic flux linkage.