Magnetic and Heating Effects

Overview

When electric current flows through a wire, it produces a magnetic field and also heat. These two effects of electric current are used in many devices like electromagnets, electric bells, heaters, and bulbs.

Key concepts

• A current-carrying wire behaves like a magnet (magnetic effect).
• A coil of wire wound on iron forms an electromagnet.
• Current passing through a wire produces heat (heating effect).
• More current and more resistance produce more heat.
• The heating effect is used in heaters, irons, and bulb filaments.

Important terms / formulae

• Electromagnet: a temporary magnet made by current in a coil.
• Heating effect: production of heat when current flows.
• Fuse: a safety wire that melts when current is too high.
• Heat produced increases with current and resistance.

Solved example or key process

1. Wind insulated wire around an iron nail.
2. Connect the ends to a battery.
3. The nail becomes magnetic and picks up pins.
4. Disconnect the battery; the nail loses its magnetism.
5. This proves the magnetic effect of current.

Important questions

1. What is an electromagnet and how is it made?
2. State two devices that use the heating effect of current.
3. How does an electric bell work?
4. Why is a fuse used in electric circuits?

Quick revision

Electric current shows two effects: it makes a magnet (used in electromagnets and bells) and it makes heat (used in heaters and bulbs). A fuse protects circuits from too much current.