ELECTRIC MOTORS, LOUDSPEAKERS/MICROPHONES

How does an electric motor work

* A current carrying wire is placed in a magnetic field
* The forces on two sides perpendicular to the field experiences forces in opposite directions
* This causes it to rotate

How do we increase the speed of the rotations

* Increase current
* Add more turns to coil
* Stronger Magnets: Increase magnetic field strength

What does a split ring commutator do

* Swaps positive and negative connections every half turn
* Direction of current swaps every half turn
* Forces acting on coil always act in the same direction
* Coil rotates in same direction each time

Do loudspeakers rely on motor effect or generator effect

Motor effect

What do loudspeakers do

Convert electrical signals into sound waves

Explain how a loudspeaker works

A.C flows through wire, magnetic field in coil

Magnetic field of coil interacts with magnetic of the magnet, exerting a force on the coil

The coil moves back/forth along the magnet

Current is alternating causing force + magnetic field to alternate

Coil and wire rapidly vibrate

Cone vibrations cause pressure vibrations in the air, which are sound waves

How is the pitch of the sound from a loudspeaker changed

* The frequency of the a.c current is altered


* Creating a different frequency of vibration in the cone

Do microphones rely on motor effect or generator effect

generator effect

What do microphones do

Convert vibrations caused by sound waves into electrical signals

Explain how a microphone works

Sound waves hit diaphragm causing it to vibrate

The wire also vibrates, moving in and out of the magnetic field

This induces a potential difference at the end of the wires, generating a current