Electricity and magnetism
What's covered
Key facts
Conductors (e.g. metals) allow current to flow easily; insulators (e.g. plastic, rubber) have very high resistance and do not conduct electricity well.
A compass contains a small magnetised needle that lines up with a magnetic field, so it is used to detect the direction of a magnetic field.
Copper is used for electrical wires because it is an excellent conductor and is ductile (it can be drawn into thin wires).
The Earth acts as a giant magnet with a magnetic field that causes compass needles to point toward magnetic north.
Electric current is the flow of electric charge (electrons) around a circuit, measured in amperes (A) using an ammeter.
An electromagnet is a coil of wire (solenoid) that becomes magnetic when an electric current flows through it; its strength can be increased by increasing the current, adding more coil turns, or adding an iron core.
Electric current is the rate of flow of electric charge around a circuit, measured in amperes (A).
Electromagnets are useful in scrapyards because their magnetism can be switched on to pick up iron and steel and switched off to drop it.
Ohm's law: voltage = current × resistance (V = I × R); this holds for conductors at constant temperature.
Outside a magnet, magnetic field lines always point from the north pole to the south pole.
Sample questions
A taste of the 22 questions in this topic, answers marked. Sign up to practise the full set with spaced repetition.
What is electric current?
- ✓Rate of flow of electric charge
- •Stored energy in a battery
- •Total amount of charge
- •Voltage in a circuit
Where is the magnetic field strongest around a bar magnet?
- ✓At the poles
- •Far from the magnet
- •In the middle
- •Inside the magnet
In a series circuit, current is:
- •Different at each component
- ✓Same at every point
- •Splits between branches
- •Zero between components
Like magnetic poles do what?
- •Attract each other
- •Cancel each other out
- •Form a current
- ✓Repel each other
In a parallel circuit, voltage across each branch is:
- •Doubled at each branch
- •Split between branches
- ✓The same as the supply
- •Zero except for one
What materials are attracted to magnets?
- •Aluminium, copper, gold
- ✓Iron, steel, nickel, cobalt
- •Water, oil, salt
- •Wood, plastic, glass
Try it for four weeks. Free.
One school. Unlimited classes. No card limit. No teacher limit. If your students aren't practising daily by the end of the trial, you owe us nothing.