Physics electromagnetism

What is the magnetic field around a wire or solenoid (coil)

Right hand thumb towards direction of current, other fingers circle to show direction

How do loud speakers work

An alternating current produces a changing magnetic field around the coil. This field interacts with the permanent magnets magnetic field which produces a force which cause is it to move up and down. This movement creates sounds

How do relays work

A current is flown through a coil and the magnetic field around a coil is used to attract a switch, causing it to pivot and close and allow a current to flow. When the current stops flowing through the coil, the switch will open

How does a d.c motor work?

A current in a circuit is flown through a coil which produces a magnetic field which interacts with the permanent magnetic field, creating a force. This force turns the coil and core, and a split ring commutator is used to reverse the current every half turn to keep the direction of rotation the same

How do you increase turning effect?

• increase the current

• increase amount of turns on the coil

• increase magnetic field strength