Faraday's Law

Faraday's Law

 

For a conductor moving in a magnetic field, the factors that affect the induced emf are:

• how quickly the magnetic field is changing
• the number of turns or loops of conductor in the field

This leads to Faraday's Law which states:

 

The induced e.m.f. is directly proportional to the rate of change of flux linkage (or rate of flux cutting)

 

A plane of wingspan 30m flies through a vertical field of strength 5 x 10^-4T. Calculate the emf induced across wing tips if its velocity = 150ms^-1.

Answer:
Calculate the area swept out each second by the wings. Multiply that by the field strength, B and you have got the flux swept out in a second.

 

So each second, 2.25Wb of flux is swept out.

 

This method leads us to a simpler equation for the emf induced by flux cutting:

E = Blv

Where:
B = magnetic flux density, T
l = length of the conductor cutting the field, m
v = speed at which the conductor cuts the field, m/s

Remember:it is only the motion perpendicular to the field that induces an emf.