HOW AN ELECTRIC GENERATOR WORKS

conductor moves relative to magnetic field, voltage is induced in the conductor. Particularly, if a coil is spinning in a magnetic field, then the two sides of the coil move in opposite directions, and the voltages induced in each side add. Numerically the instantaneous value of the resulting voltage (called electromotive force, emf) is equal to the minus of the rate of change of magnetic flux Φ times the number of turns in the coil: V=−N•∆Φ/Δt. This relationship has been found experimentally and is referred to as Faraday's law. The minus sign here is due to Lenz law, which states that the direction of the emf is such that the magnetic field from the induced current opposes the change in the flux which produces this emf. Lenz law is connected to the conservation of energy.

For clarity in the above animation a single rectangular conductor loop is shown instead of an armature with a set of windings on an iron core. Since the rate of magnetic flux change through the coil that spins at a constant rate changes sinusoidally with the rotation, the voltage generated at the coil terminals is also sinusoidal (AC). If an external circuit is connected to the coil's terminals, this voltage will create current through this circuit, resulting in energy being delivered to the load. Thus, the mechanical energy that rotates the coil is converted into electrical energy. Note that the load current in turn creates a magnetic field that opposes the change in the flux of the coil, so the coil opposes the motion. The higher current, the larger force must be applied to the armature to keep it from slowing down. In the animation the coil is rotated by the hand crank. In practice, the mechanical energy is produced by turbines or engines called prime movers. In a small AC generator a prime mover is usually a rotary internal-combustion engine. In commercially available devices an alternator is integrated with this engine into a single appliance. The resulting device is referred to as engine-generator set or genset, although casually it is often called just a generator. A genset is the most common and the cheapest emergency backup power source for a home or business. 

ELECTRIC GENERATORS: HOW THEY WORK

 
Operation of power generators is based on the phenomenon of electromagnetic induction: whenever a