Magnets 2,000 years ago Greeks discovered deposits of a mineral that was a natural magnet. It was found in the region of Turkey called Magnesia. So the material was given the name magnetic.

Twelfth century Chinese sailors used the material to make compasses which helped improve navigation. Today the word magnetism refers to properties and interactions of magnets.

All magnets have a north and south pole. Even horseshoe or disk magnets. The magnetic field lines are closest together at the ends of the bar magnet.

Magnets exert a force on each other. Depending on which ends of the magnets are close together, the magnets either repel or attract each other.

Compass needles placed around a bar magnet line up along magnetic field lines. A compass can help determine direction because the north pole of the compass needle points north.

A magnet is surrounded by a magnetic field. This field exerts a force on other magnets and objects made of magnetic material. It is the strongest closest to the magnet and gets weaker far away.

The north pole of a magnet is defined as the end of the magnet that points toward the geographic north. Because opposite magnetic poles attract, the north pole of a compass is being attracted by a south magnetic pole.

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The Earth’s magnetic pole moves slowly over time and sometimes they switch places. The poles have switched 150 times in the past seventy million years.

So Earth is like a bar magnet with its south magnetic pole near its geographic north pole. Currently Earth’s south magnetic pole is located in northern Canada about 1500 km from the geographic north pole.

Certain groups of atoms with aligned magnetic poles are called magnetic domains. An iron nail has enormous number of magnetic domains, but is not magnetic. Why?

The poles of the domains are arranged randomly and point in different directions. So all the magnetic fields cancel each other out. But you can make them a temporary magnet by placing the nail or paper clip on a magnet. It’s poles align and you get a temporary magnet.

An electromagnet is a temporary magnet made by wrapping a wire coil carrying a current around an iron core. Examples: Loudspeakers, stereo speakers

The magnetic properties of an electromagnet can be controlled by changing the current in the coil. A galvanometer uses an electromagnet to measure electric current.

In a simple electric motor, an electromagnet rotates between the poles of a permanent magnet. A electric motor changes electrical energy into mechanical energy The parts of a simple electric motor are a wire coil, a permanent magnet and a source of current, like a battery. Examples: Fans, hair dryer, CD players

An electric current is produced by moving an wire loop through a magnetic field or a magnet through a wire loop. A generator can produce an electric current rotating a wire coil in a magnetic field.

A direct current flows in one direction. (DC) An alternating current changes direction in a regular pattern. (AC)

A transformer changes the voltage of an alternating current. The voltage can be increased or decreased. The changing magnetic field in the primary coil of a transformer induces an alternating current in the secondary coil.

Energy cannot be created or destroyed, but can only be transformed from one form to another.

Petroleum, natural gas and coal are fossil fuels formed by the decay of ancient plants and animals. Petroleum is a mixture of thousands of chemical compounds, most of which are hydrocarbons.

About 90 percent of all coal used in the United States is burned by power plants to produce electricity. Power plants turn fossil fuels to produce steam that spins turbines attached to electric generators.

Nuclear power plants produce about eight percent of the energy used each year in the United States. Nuclear reactors use the energy released in the fission of U-235 to produce electricity.

The energy released in the fission reaction is used to make steam. The steam drives a turbine that rotates an electric generator. Nuclear power generation produces high- level nuclear waste.

Organisms could be damaged if radiation is released from the reactor. Nuclear waste is a radioactive by-product produced by using radioactive materials.

The development of alternative energy sources can help reduce the use of fossil fuels. Photovoltaic cells or solar cells, convert radiant energy from the Sun into electrical energy. Producing large amounts of energy from solar cells is more expensive than using fossil fuels.

Hydroelectric power plants convert the potential energy in water to electrical energy Tidal energy, wind energy and geothermal energy can be converted into electrical energy, but are useable only in certain locations

Alternative fuels such as hydrogen could be used to power cars, and biomass can be burned to provide heat.