# Magnetism

## Physical Science - Middle School

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Magnetism What Is a Magnet? A magnet is a substance that attracts the element iron or materials that contain iron. All magnets have opposite ends called the north pole and the south pole. Similar magnetic poles repel each other, and opposite poles attract each other. N S magnetic domains magnetic non- magnetic Earth’s Magnetic Field Deep in the Earth, convection currents in the liquid iron core create a magnetic field that impacts the Earth’s magnetism. The Earth acts like a giant magnet, having two opposite poles and a strong magnetic field. The Earth’s geographic poles are at a slightly different location than the Earth’s magnetic north and south poles. The positions of the magnetic poles are dynamic and shift from year to year. Electromagnetism When an electric current flows through a coil of wire, a magnetic field is produced. This relationship between electricity and magnetism is called electromagnetism. Unlike bar magnets, which are permanently magnetized, the magnetism of an electromagnet can be controlled by switching the electric current on or off. Inside a Magnet Inside a magnet there are clusters of atoms known as magnetic domains that are responsible for magnetic properties. If the atoms with similar magnetic fields within a domain line up in the same direction, they are said to be magnetized. Atoms that are arranged in random directions within a domain are considered to be non-magnetic. Natural elements that can be magnetic include iron, nickel, cobalt, gadolinium, samarium and neodymium. Magnetic Forces, Poles & Fields The degree to which magnets repel or attract each other depends on their magnetic forces. The greatest magnetic force is located at the poles of a magnet, but there is an area all the way around the magnet that displays magnetism. This area is called its magnetic field. The lines in the diagram represent the magnetic force around the magnet. The closer the lines are, the greater the force. The arrows show the direction of the field. © Copyright NewPath Learning. All Rights Reserved. 94-4495 Visit www.newpathlearning.com for Online Learning Resources. N S magnetic eld magnetic eld greatest magnetic force Electromagnets are used in many devices including computers, doorbells and cranes. + ALKALIN E BA TTER Y switch coils iron core wire current from battery NS NS N S N S similar poles repel opposite poles attract NS NS N S N S similar poles repel opposite poles attract similar poles repel opposite poles attract N S Magnetic North Magnetic South North Pole South Pole magnetic eld magnetic eld
Magnetism Pause and Review Label the magnetic poles, and the areas of greatest and least magnetic force. © Copyright NewPath Learning. All Rights Reserved. 94-4495 Visit www.newpathlearning.com for Online Learning Resources. Label the parts of the electromagnet. How are electromagnets different from bar magnets? ______________________________________________________________________ ______________________________________________________________________ + ALKALIN E BA TTER Y