Electromagnetic Induction Flashcards
Define magnetic flux
The magnetic flux through a plane surface is the product of the component of the magnetic flux density normal to the surface and the area of the surface.
Φ = BAcosθ
Define magnetic flux linkage
The magnetic flux linkage through a loop is the product of the magnetic flux through the loop and the number of turns in the loop.
Magnetic flux linkage = NΦ = NBAcosθ
Define Faraday’s Law
Faraday’s Law states that the magnitude of the emf induced is directly proportional to rate of change of magnetic flux linkage.
emf = - dNΦ/dt
Define Lenz’s Law
Lenz’s Law states that the e.m.f is induced in the direction such as to oppose the flux linkage that is inducing it.
Formula for electromagnetic induction in straight conductors
emf = BLv
Describe motional electromotive force in straight conductors
If the conductor moves at velocity v at right angles to the field, then the electrons in it would also be moving at velocity v across the field. By Fleming’s Left Hand rule, each electron would experience a magnetic force downwards, forcing it to migrate to the lower end of the conductor.
The movement of the electrons results in an accumulation of negative charges at one end and positive charges at the other end. This sets up an electric field E along the rod.
The accumulation of electrons continues until the force on each electron due to the electric field and the magnetic field are balanced. At a steady state, an e.m.f. is induced between the ends of the conductor.
Formula for electromagnetic induction in rotating discs
emf = 1/2 Br^2ω
What are the negative impacts of eddy currents and how to reduce them?
Eddy currents formed in conductors, such as the iron core of a transformer, may cause significant heat generation and loss in efficiency. The effect of eddy currents may be reduced by effective lamination which limits the amount of eddy current generated.
