Magnetism – Learning Outcomes Discuss the nature of magnets. Demonstrate the properties of magnets. Plot the magnetic field of a bar magnet. Demonstrate the Earth’s magnetic field.

Nature of Magnets Magnets will only attract ferromagnetic materials – iron, nickel, cobalt, and some alloys of these. Magnets are strongest at the ends, called poles. Magnets always have two poles, north (red) and south (blue or black). Cutting a magnet in half creates new poles.

Nature of Magnets If allowed to rotate freely, a magnet will line up north-south with the Earth. Like poles repel, unlike poles attract. Magnets can create magnetism in ferromagnetic materials.

Magnetic Fields A magnetic field is the space around a magnet where it has a magnetic effect.

To Plot a Magnetic Field Place a bar magnet on a piece of paper. Place a plotting compass near the magnet. Make a pencil mark at the ends of the compass needle. Move the compass so that its needle is pointing towards a dot. Mark the other end of the needle.

To Plot a Magnetic Field Repeat moving the compass and marking the needle position. Join the dots with a curve and repeat for another field line.

Earth’s Magnetic Field The Earth has a magnetic field due to its molten iron core. We pretend it has a bar magnet in its core with the south magnetic pole at the north geographic pole and the north magnetic pole at the south geographic pole.

To Demonstrate the Earth’s Field Hang a bar magnet horizontally in a paper stirrup from a retort stand. Rotate the magnet and let it come to rest a few times. Note the orientation of the magnet each time. Note the poles on the magnet using a compass. Repeat for another magnet.

To Demonstrate the Earth’s Field