The working of a speaker is similar to a tuning fork, whenever the tuning fork is striken, a humming sound can be heard. This sound is created by the compression and rarefaction of air particles, around the vibrating fork arms. When these compressions and rarefactions hit the eardrumit vibrates and we percieve sound. In a speaker , this compression and rarefaction is performed by a paper diaphragm that vibrates in accordance with the electrical signal fed to it.

The is extremely light when compared to other electrical devices. At the base is a powerful ring magnet. Inthe centre is a voice ciol made up of a fine,wound around a paper cylinder.

This speaker works on the principle of mechanical effect of current proposed by Ampere. "Whenever a current carrying conductor is placed in the magnetic field it experiences a mechanical force. The direction of the force is perpendicular to the direction of both the magnetic field and the current flowing through the condutor."

As the diaphragm vibrates the air molecules surrounding the speaker vibrate producing sound. Now the sound's frequency is similar to the original frequency.

An electric motor is a device which converts electrical energy into mechanical energy. It also works on the principle of mechanical effect of current.

It generally consist of a field magnet,a rotating armature,rings split and carbon brushes. The field magnet is a powerful magnet. The armature is capable of rotating around its own axis. The split rings are also known as commutators. They can rotate with the coil. The carbon brushes are connected with the battery.When the current is passed, the coil rotates in accordance with the electrical energy.

The interaction of the electrical enrgy and the magnetic field with the coil produces the mechanic effect.

A transformer is an electrical device used to transfer electrical energy from one circuit to another.It i used to step up or step down the ac voltage of current.