Electromagnetic Induction. emf is induced in a conductor placed in a magnetic field whenever there is a change in magnetic field. Moving Conductor in a Magnetic Field. Consider a straight conductor moving with a uniform velocity, v , in a stationary magnetic field.
E = Blv.
E = E It = W
Unit : weber (Wb)
The ‘-’ sign indicates that the induced e.m.f. acts to
oppose the change.
Back emf, Eb
Driving source, VBack emf and Power
0Variation of current as a motor is started
0Variation of current with the steady angular speed of the coil in a motor
0Variation of output power with the steady angular speed of the coil in a motor
The magnetic flux linkage in a coil the current flowing through the coil.
Where L is the constant of proportionality for the coil.
L is numerically equal to the flux linkage of a circuit when unit current flows through it.
Unit : Wb A-1 or H (henry)
Lis numerically equal to the emf induced in the circuit
when the current changes at the rate of 1 A in each second.
+emf across contacts at break
The energy originally stored
in the magnetic field of the coil
is now stored in the electric
field of the capacitor.