Physics · Both
Magnetism & Electromagnetism
Magnetic fields, electromagnets, the motor effect and electromagnetic induction basics.
Magnets have north and south poles. Electric currents create magnetic fields – this is the basis of electromagnets, motors and generators.
Magnetic fields
• Field lines go from north to south outside a magnet
• Closer lines = stronger field
• Like poles repel; opposite poles attract
• Earth’s magnetic field – compass needles point north
A **magnetic field** is the region where a magnetic force acts.
Electromagnets
A current in a wire produces a magnetic field.
A coil (solenoid) with a soft iron core makes a strong electromagnet.
Advantages over permanent magnets: can be switched on/off; strength controlled by current / number of turns.
Motor effect and induction
**Motor effect:** a current-carrying wire in a magnetic field experiences a force (if the field and current are not parallel).
Direction given by Fleming’s left-hand rule (Higher).
**Electromagnetic induction:** a changing magnetic field through a coil (or a wire moving in a field) can induce a potential difference / current.
Basis of generators and transformers.
Practice questions
Try these without looking at the answers first.
Q1.Which poles attract?
Show answer
Opposite poles (N and S)
Q2.How can you make an electromagnet stronger?
Show answer
More current / more turns / iron core
Q3.What does a generator use to produce electricity?
Show answer
Electromagnetic induction / moving magnet or coil