Electromagnetism Flashcards
Equation linking Flux (Φ) and Flux density (B)
Flux = Flux density * Area
Φ = B * A
Units for Flux (Φ)
weber (Wb)
Units for Flux density (B)
weber per meter squared (Wb/m^2)
Definition of magnetic flux?
A measure of how much of a magnetic field passes perpendicularly through an area.
Equation for flux linkage?
flux linkage = no. coils * flux through one coil
Unit conversion between Volts, Webers and Joules?
1V = 1Wb/s = 1J/C
What is Lenz’s law?
The direction of induced emf is such as to oppose the change that cause the induced emf.
Equation for Faraday’s law of electromagnetic induction?
induced emf, ε = -ⅆ(N∅)/ⅆt
Equation linking Force, Current, Magnetic field and length?
F = BIL sin θ
Why does an electromagnetic machine need good conductance?
Conductance affects current and current is proportional to magnetic flux .
Define conductance and state the equation for it:
A measure of the ability of how easily a current can flow through a material.
Define permeance:
The ability for a material to conduct magnetic flux well.
Define eddy currents:
A current induced in the core of a transformer due to changing magnetic flux according to Faraday’s law of induction.
What is a transformer?
An electromagnetic machine which transforms voltages by inducing emf without physical movement, with an AC supply.
What is a generator?
Sn electromagnetic machine that uses rotation to produce the flux change needed to induce an emf.
