SOUND
we can transform electric current into sound by using electromechanical devices, such as bells and buzzers.


ELECTROMAGNETIC MECHANISMS
Are devices that can convert movement into electricity or vice versa.

ELECTROMAGNETIC GENERATORS 
Transform mechanical energy into electricity:

Dynamos
A dynamos consist of a magnet and a rotary coil. The coil is located between the two poles of the magnet. The ends of the coil have tow semi-circulaar conductors, which form the commutator. These conductors are attached to carbon brushes, which in turn are conected to electrical wires. When electricty is applied to the coil, it rotaters and begins to generate direct current in the coil.



Alternators
A simple alternator is almost identical to a dynamo, except for the commutator, which consist of two metallic rings connected to carbon brushes, Instead of direct current, this produces altenating current.


ELECTRIC MOTORS
An electric motor is a device that can transform electrical energy into movement. It uses the forces of attraction and repulsion between a magnet and an electrically-charged wire.


RELAYS
A relay is an elctromagnetic component that works as a switch. When electricity passes through the coil, it acts like a magnet. The coil attracts a moveable metal contact towards another fixed contact. When the electricity stops flowing, the moveable contact goes back to its original position.