Magnetic Fields

Why does a compass needle point north?

• The compass is a bar magnet

• Because north is up and you know that up is always north or the stratosphere.

• Because it's magic

• Because the North end of the compass lines up with the Earth's magnetic south pole

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Magnetic force between two magnets gets weaker the more ________________ between them.

• distance

• attraction

• metal

• lightsabers

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A ________ is a device that has a magnet on a needle that spins freely. It is used for navigation because its needle usually points north.

• calculator

• ruler

• compass

• map

What causes the magnetic field to form in an electromagnet?

• Electromagnets are only called magnets because electricity is involved.

• The domains of the magnet become aligned

• The magnetic field is absorbed from another magnet

• Electric current flowing in a wire

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You can cause a permanent magnet to lose its magnetic field if

• You forcefully vibrate the object, causing its domains to fall out of alignment.

• By rubbing an iron object with a permanent magnet in the same direction repeatedly.

• You freeze the object.

• You connect the north and south poles of two magnets.

Magnetic fields are strongest

• between the poles

• at the north pole

• at the south pole

• at both poles

A magnet must always have two poles, even if cut in half, because

• A magnet is made up of tiny magnetic domains that are aligned.

• Each pole divides in half and the magnetic field becomes weaker.

• Magnetic domains are out of alignment.

Permanent magnets are made out of the following materials

• Copper, Chromium, and Cobalt

• Iron, Cobalt, and Silver

• Nickel, Cobalt, and Iron

• Copper, Nickel, and Iron

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An electromagnet can be strengthened if

• less coils are added to the iron core

• the iron core is removed

• more current runs through the wire

• a nickel or cobalt iron core is used.

Which of the following statements is true about Earth’s magnetic poles?

• They are the areas where Earth’s magnetic field is strongest.

• They are located at Earth’s geographic poles.

• They are the areas where Earth’s magnetic field is weakest.

• Earth has four magnetic poles.