Everything Science Grade 12

13.2 CHAPTER 13. ELECTRODYNAMICS

If the current flowing inthe conductor were plotted as a function of theangle between
the plane of the conductor and the magneticfield, then the currentwould vary as
shown in Figure 13.2. The current alternates about zero and is known asan alternating
current (abbreviated AC).

time

current (arbitrary units)

Figure 13.2: Variationof current as the angleof the plane of a conductor with the
magnetic field changes.

Recall Faraday’s Law which you learnt about in Grade 11:

DEFINITION: Faraday’s Law

The emf (electromotiveforce), �, produced around a loop of conductor

is proportional to the rate of change of the magnetic flux, φ, through

the area, A, of the loop. This can be stated mathematicallyas:

� =−N

Δφ

Δt

where φ = B· A and B is the strength of the magnetic field.

Faraday’s Law relates induced emf (electromotive force) to the rate of change of flux,
which is the product ofthe magnetic field andthe cross-sectional areathe field lines
pass through. As the closed loop conductor changes orientation withrespect to the
magnetic field, the amount of magnetic flux through the area of the loopchanges, and
an emf is induced in theconducting loop.