physics
𧲠Magnets
Permanent magnet
A magnet that does not lose its magnetism.
Temporary magnet
A magnet that can gain and lose magnetism easily (only magnetic in a field or with current).
Magnetic domain
A region where atoms are aligned in the same direction.
How to make a permanent magnet
Stroke steel with a magnet in one direction
Use a strong magnetic field (electromagnet)
β‘ Electromagnets
Three things needed:
Iron core
Coil of wire
Electric current
Magnetic field direction (2 methods):
Right-hand grip rule
Compass
β ALSO: iron filings (shows field pattern)
π Electric Bell (IMPORTANT β exam question)
Circuit is switched on
Current flows β electromagnet becomes magnetic
Electromagnet pulls the armature
Striker hits the bell
Movement breaks the circuit
Electromagnet turns off
Armature returns β circuit reconnects
Process repeats rapidly
π This is a make-and-break circuit
β D.C Motor
How it works:
Current flows through a coil in a magnetic field
The coil becomes magnetic
Forces act on opposite sides β rotation
How to make a motor stronger:
Increase current β
Add more coils β
Use stronger magnets β
Increase voltage (stronger battery) β
π Batteries
Battery
A device that converts chemical energy into electrical energy
Electrodes
Two different metals (positive and negative)
Electrolyte
Liquid that allows charge to flow
Why must metals be different?
They must have different reactivity
This creates a potential difference (voltage)
π Electricity Basics
Conductor
Allows electrons to flow easily (e.g. metals)
Insulator
Does not allow electrons to flow (e.g. plastic)
Current
The flow of electric charge (electrons)
Measured with: Ammeter
Unit: Amps (A)
β‘ Voltage & Circuits
Voltage (Potential Difference)
The energy transferred per charge / βpushβ of electrons
Measured with: Voltmeter
Unit: Volts (V)
Voltmeter connection:
β Parallel
Ammeter connection:
β Series
π Parallel Circuits
Voltage:
Same across all branches
Current:
Splits between branches