Electromagnets

A compass needle points north because of Earth's magnetic field unless

• it is close to a wire with a current

• it is close to any wire

• it is close to a battery

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The electromagnetic forces from a current carrying wire are strong enough to move the compass needle. The forces can be made stronger by

• making the wire shorter

• making the wire longer

• making the wire into loops

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An electromagnet is a magnet that

• its strength can be varied and turned on and off

• always has a magnetic field around it

• has very little strength

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Permanent Magnets and Electromagnets are similar in which TWO ways?

• it can be turned off and on

• they both have a north and south pole

• they are surrounded by a magnetic field

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Bob made an electromagnet but it was very weak.  How can he make it stronger?

• take away a d-cell
• wrap the wire loosely
• use thicker wire
• use less winds

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Which rule explains why you would not use a brass rivet to make an electromagnet?

• opposites poles attract
• only iron and steel can become magnetized
• electricity flows from positive to negative
• metals conduct electricity

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How could the strength of an electromagnet be increased?

• by decreasing the amount of current in the electromagnet

• by increasing the number of coils in the wires of the electromagnet

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

1) A wire carries a current, creating a magnetic field around itself as shown. The current in the wire is:

• A. Directed to the right

• A. Directed to the left

• A. Equal to the magnetic field

• In the same direction as the magnetic field

1) A bar magnet is at rest, next to a fixed electromagnet. In which direction will the bar magnet move when switch S is closed?

• to the left

• to the right

• up the page

• down the page