Have you ever put a picture on the refrigerator? Have you used a key card to unlock a hotel room door, listened to music through speakers, or saved information on a computer? All of these tasks, and many more, are made possible by magnets.

Question

Magnets come in different shapes and sizes. The magnets in a computer are thinner than a human hair. The magnets on industrial cranes can be several feet across. But all magnets have the same basic properties. A magnet is something that has a magnetic field—an area that exerts magnetic force. This force can attract metal or other magnets. It can also push other magnets away. The stronger the magnet, the more force the magnetic field exerts.

Which of these exerts the most magnetic force?

A
A compass needle that points north but doesn’t attract objects

B
A freezer door that uses magnets to stay shut

C
A refrigerator magnet that holds up two pieces of paper

D
A junkyard crane that uses magnets to pick up cars

Answer 1

The option that exerts the most magnetic force is:

D: A junkyard crane that uses magnets to pick up cars.

Junkyard cranes use powerful electromagnets to lift heavy metal objects, such as cars, which require significant magnetic force. The other options involve much weaker magnets that are not designed for lifting heavy objects.