When current flows through a wire a magnetic field is produced around the wire. The strength of the magnetic field depends on the size of the current. If the direction of the current is reversed the direction of the magnetic field is reversed
Right Hand Rule
With your right hand point thumb in the direction of conventional current, the direction of magnetic field will be the direction of other fingers
Solenoid
A solenoid is a coiled wire. When current is passed through a solenoid the magnetic field is uniform and strong inside the solenoid.
Increasing Strength
- Increase current
- Increase turns in the coil
- Add iron core to make an electromagnet
Electromagnetic devices
Relay Using a switch for high voltage circuits is dangerous so the switch is replaced by 2 metal contacts with one attached to a spring. There is a low voltage circuit with an electromagnet which is safe to use a switch on, when it is turned on the electromagnet attracts the magnet on the spring so the metal contacts come together completing the circuit