Magnets and Their Properties

Magnets and Electricity

• The earliest magnets were lodestones, rocks with magnetic qualities, studied by ancient Chinese and Greeks who believed they had medical uses.
• There are five types of magnets: bar, cow, horseshoe, disk, and electromagnet, with the best magnets made of an alloy called alnico (aluminum, nickel, and cobalt).
• Magnets are made of atoms that act like miniature magnets with north and south poles, and can be made by placing magnetic materials in a strong field of direct current electricity.
• The strongest magnets have most of the domains lined up, and are used in thousands of electrical devices, including TVs and telephones.
• Electromagnets are the most useful type, as they can be turned on and off.

Electricity Generation

• Electricity and magnetism are closely related, as magnets and wires in motion can generate electricity.
• Most electricity is generated by moving a coil of wire inside a magnetic field, which can be generated by steam or falling water turning a turbine.
• Other ways to generate electricity include using crystals, solar cells, thermocouples, and chemical reactions.
• Some states generate over half their electricity using nuclear energy, which is clean, cheap, safe, and available long after other resources run out, but also produces harmful radiation and may contaminate water supplies.

Electric Circuits

• Current electricity is a flow of electrons through a conducting circuit, similar to a flow of water through a pipe.
• Materials like copper are good conductors of electricity, while materials like glass are insulators.
• Batteries and light bulbs can be connected in series or parallel, with different effects on voltage and brightness, and parallel circuits are commonly used in houses.