1. Electro Mechanical System
Faraday’s Law
If the flux linking a loop (or turn) varies as a function of time, a voltage is induced between its terminals.
The value of the induced voltage is proportional to the rate of change of flux.
Where:
E = induced voltage [V]
N = number of turns in the coil
 = change of flux inside the coil [Wb]
t = time interval of the flux changes [s]
Lecture 02
Electro Mechanical System

2. Electro Mechanical System
Faraday’s Law
Example:
A coil of 2000 turns surrounds a flux of 5 mWb produced. by a permanent magnet.The magnet is suddenly withdrawn causing the flux inside the coil to drop uniformly to 2 mWb in 1/10s. What is the induced voltage?
Lecture 02
Electro Mechanical System

3. Voltage Induced in a Conductor
It is often easier to calculate the induced voltage on a segment of conductor instead of the voltage on a coil
E = B l v
 Where:
  E = induced voltage [V]
B = flux density [T]
l = active length of conductor in the magnetic field [m]
v = relative speed of the conductor [m/s]
Lecture 02
Electro Mechanical System

4. Voltage Induced in a Conductor
Example:
A stationary conductor of a large generator have an active length of 2m and are cut by a field of 0.6 teslas, moving at a speed of 100m/s. Calculate the voltage induced in each conductor.
Lecture 02
Electro Mechanical System

5. Lorentz Force on a Conductor
A current-carrying conductor sees a force when placed in a magnetic field
Fundamental principle for the operation of motors.
The magnitude of the force depends upon orientation of the conductor with respect to the direction of the field.
Force is greatest when the conductor is perpendicular to the field.
The Lorentz or electromagnetic force:
F = B l I Sin
Where:F = force acting on the conductor [N]
B = flux density [T]
l = active length of conductor in the magnetic field[m]
I = Current in the conductor [A]
 = Angle between the flow directions of current & flux
Lecture 02
Electro Mechanical System

6. Lorentz Force on a Conductor
Example:
A conductor 3 m long is carrying a current of 200 A and is placed in a magnetic field with a density of 0.5 T. Calculate the force on the conductor if it is perpendicular to the lines of flux.
Lecture 02
Electro Mechanical System

7. Direction of Force on Conductor
Current carrying conductor is surrounded by a magnetic field.
The flux lines of two magnetic fields never cross each other.
The flux lines of two magnet fields are vectorally added.
The generated mechanical force tends to push the lines of flux back to an even distribution.
Right hand rule
Point fingers in the direction of current flow (+ve to - ve).
Bend fingers into the direction of the magnetic field (N to S).
Thumb points in the direction of force .
Lecture 02
Electro Mechanical System