Unit 4: Magnets

Which of the following is true of all magnets?

• They are man-made.

• They are made of iron.

• They have two poles and a magnetic field.

• They are magnetic only when an electric charge goes through them.

If you have two magnets and you try to put the two north poles together, what will most likely happen?

• The two poles will not touch each other because of magnetic repulsion.

• The magnets will stick together because of magnetic attraction.

• The two poles will touch but not stick together.

• The magnets will lose their magnetism.

Which of the following objects has polarity?

• the Earth, which has magnetic north and south poles

• the city of Chicago, which has a North and South side

• a map of the country, which has a compass pointing north

• an unmagnetized block of metal, which has a top and a bottom

A magnetic field is_____________.

• something used to demagnetize pieces of metal

• the area in which a magnet exerts magnetic force

• an open area where you are likely to find natural magnets

• an electric charge that can be sent through a wire to make it magnetic

True or False: Man-made magnets always retain their magnetism.

• True

• False

Which of the following works because of the Earth's magnetism?

• a compass

• a maglev train

• an electric lock

• a computer chip

Magnetic attraction is a property that makes two magnets stick together. It occurs when _____________________.

• a magnet is near a nonmagnetic object.

• two magnets' south poles are near each other.

• opposite poles of two magnets are near each other.

• a natural magnet and a man-made magnet are near each other.

Magnets are a mystery to scientists because scientists

• don't know how to tell the north pole from the south pole

• can't tell how much magnetic force a magnet has

• don't know why magnets have magnetic force

• don't know why the Earth has magnetism

Each of the following is an example of how magnets are used except

• storing information on computer hard drives

• sticking photos on the refrigerator

• making high speed trains levitate

• lock padlocks with metal keys

_____________________ is an object that attracts iron and a few other metals.

• Magnet

• magnetic field

• motor

• electromagnet

• magnetic pole