Lesson 21.2: Current can produce magnetism

Lesson Focus

Discover the powerful link between electricity and magnetism. We'll explore how electric currents create magnetic fields and how this principle powers technologies, from simple electromagnets to the complex motors that move our world.

Learning Objectives

• Describe how an electric current produces a magnetic field.
• Identify and describe several practical uses for electromagnets.
• Examine how electric motors use magnets to create motion.
• Observe how to make a simple electromagnet in a hands-on experiment.

Phenomenon: A compass needle moves near a wire with electricity.

Cause: Moving electric charges.

Mechanism: An electric current, which is moving electrons, generates a magnetic field around the wire. This is electromagnetism. The field direction depends on the current's direction.

Phenomenon: A looped wire is a stronger magnet. Cause: Concentrating the magnetic field. Mechanism: Winding a wire into a coil makes the magnetic fields from each loop add up inside. This creates a north and south pole, just like a bar magnet. Result: A stronger, more focused magnetic field. Takeaway: More loops mean more magnetic power.

Phenomenon: A nail wrapped in a current-carrying wire picks up paperclips.

Cause: Adding an iron core.

Mechanism: The coil's magnetic field aligns the magnetic domains inside the iron, adding its magnetism to the coil's.

Phenomenon: Cranes lift scrap metal; computers save files.

Cause: Controllable magnetism.

Mechanism: An electromagnet turns on to attract metal or orient tiny magnets on a disk (storing data). Turning the current off releases the metal or sets the data.

Phenomenon: A fan spins when plugged in.

Cause: An electric motor.

Mechanism: An electromagnet spins because it is pushed and pulled by a permanent magnet. A part called a commutator reverses the current every half-turn, which keeps the force going in the same direction.