What do permanent magnets always have?

A single north pole from which magnetic field lines radiate Two poles — a north pole and a south pole — that cannot be separated Positive and negative ends, like a battery One pole that alternates between north and south

What is Earth's magnetic field, and why does a compass work?

Earth has a magnetic north pole at its geographic North Pole — compass needles are repelled away from it Earth has a magnetic field (generated by its liquid iron core) with a magnetic south pole near the geographic North Pole — a compass needle's north pole is attracted to it Compasses work because they are attracted to the iron in Earth's crust, not a magnetic field Earth's magnetic field is produced by its rotation, not its core

Hans Christian Oersted made a landmark discovery in 1820. What did he observe?

A magnet moving near a wire produces a spark — magnetism creates electricity A current-carrying wire deflects a nearby compass needle — showing that electric current creates a magnetic field Two current-carrying wires always attract each other regardless of current direction A charged rod spinning rapidly becomes magnetic

Michael Faraday discovered electromagnetic induction in 1831. What is electromagnetic induction?

A static magnetic field continuously produces current in a wire An electric current always produces a magnetic field in the space around it A changing magnetic field induces (creates) an electric current in a nearby conductor Magnetic fields induce electric charges on the surface of metals

An electric motor converts electrical energy into mechanical energy. Which principle makes this possible?

A motor works because moving the wire creates a current that pushes the motor A current-carrying wire in a magnetic field experiences a force (the motor effect) Electrical energy is converted to thermal energy which expands to push the motor A motor works by electrostatic repulsion between charged coils

An electrical generator converts mechanical energy into electrical energy. Which principle makes this possible?

Friction from rotating parts creates static electricity that is collected Rotating a coil in a magnetic field continuously changes the magnetic flux through it, inducing a current (electromagnetic induction) The generator splits water molecules into hydrogen and electron flow Magnetic fields from the generator's coil push electrons through the external circuit

A transformer changes the voltage of an alternating current supply. What principle allows it to work?

Transformers work by chemically converting high-voltage electricity into low-voltage electricity Electromagnetic induction — the changing AC current in the primary coil creates a changing magnetic field that induces a voltage in the secondary coil Transformers use resistors to reduce or increase voltage Transformers only work with DC (direct current) because AC constantly reverses

James Clerk Maxwell published his equations of electromagnetism in 1865. What did they predict?

Electric charges can travel faster than the speed of light Magnetic monopoles must exist to complete the theory Electromagnetic waves travelling at exactly the speed of light — strongly suggesting that light itself is an electromagnetic wave Electricity and magnetism are fundamentally different forces with no connection

Why is it efficient to transmit electricity over long distances at very high voltages?

High voltage electricity travels faster through cables, reaching homes before it loses energy Higher voltage means lower current for the same power (P = IV), and lower current means less energy lost as heat in the cables (P_loss = I²R) High voltage reduces the resistance of the cable High voltage prevents electrons from colliding with each other in the wire

Which statement best summarises the relationship between electricity and magnetism?

Electricity causes magnetism, but magnetism cannot produce electricity They are completely separate forces that happen to share similar mathematical laws They are two aspects of a single force — electromagnetism — related by the fact that changing one always produces the other Magnetism is a stronger version of electricity that only acts on metals