Lesson 21.3: Magnetism can produce current

Lesson Focus

We've seen how electricity creates magnetism. Now, we'll discover the reverse: how moving magnets can generate electric current, a principle that powers everything from hand-crank chargers to the grid that lights our homes.

Learning Objectives

• Explore how moving a magnet or wire through a magnetic field can generate an electric current.
• Learn how generators work by converting the energy of motion into useful electrical energy.
• Compare direct current (DC), which flows in one direction, with alternating current (AC), which regularly reverses direction.

A moving magnetic field can create electricity.

This phenomenon occurs when a wire crosses magnetic field lines, a process that induces an electric current. Whether the magnet moves or the wire moves, the effect is the same.

This principle, electromagnetic induction, shows that motion is key to generating electricity from magnetism.

A generator transforms kinetic energy into electrical energy.

When an external force spins a coil of wire inside a magnetic field, the wire continuously crosses magnetic field lines.

This constant motion generates a steady electric current.

Electric charge flows in two distinct ways.

Direct Current (DC) is a one-way flow of electrons, like the power from a battery. In contrast, Alternating Current (AC) is a flow that periodically reverses direction, like the power from wall outlets.

Many devices must convert the AC from your home into DC.

The type of current produced depends on the generator's internal design.

An AC generator uses a simple rotating coil, causing the current to reverse direction with each half-turn.

A DC generator adds a part called a commutator, which acts as a reversing switch to keep the current flowing in one direction.

A transformer increases or decreases the voltage of an alternating current.

It uses two wire coils; if the second coil has fewer loops than the first, it's a step-down transformer that decreases voltage.

This allows high-voltage electricity from power lines to be safely reduced for use in homes and businesses.