· This is a statement saying that:

ü
*The induced electromagnetic
force across a conductor is proportional to the rate at which the conductor
cuts magnetic flux. *

· We can use SI units to equate the emf to the rate at which the flux is cut.

·
The work done by the force exerted on a wire by a field
is Force * Distance. The force, as we already know, is *BI**l*, so energy supplied *E = BIlx*. The definition of the electromotive
force E as the energy *E*
changed from other forms of energy to electrical energy per unit charge *Q*
gives

*E = Q *E. Charge *Q*
is the product of current and time so

*E = *E I t. Combine these two
equations:

__E It = BI__* lx*, so

ü
_{E = }__Blx__

t

· Lenz's Law states that

·
*The direction of any induced
current is such as to oppose the flux change that causes it.*

· This means that the emf produced must be negative, as the voltage causing it is taken to be positive, as is the field that it produces, which in turn causes the emf.

· As Blx is the magnetic flux, we can express this as

ü
_{E = - }__F__

t

·
Or if, according to the original statement,
the emf is proportional to the **rate of change of flux**, calculus notation
can be used to produce:

ü
_{E = - }__d____F__

dt

· REMEMBER THIS, IF NOTHING ELSE IN LIFE!

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