Electromagnets

Arrows are close together on a force field when the force is

• stronger

• weaker

• opposite

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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

What THREE ways are electromagnets different from permanent magnets?

• they can be turned off and on

• they can increase in strength by increasing the current in the wire

• they are smaller in size

• they can change which is the north and south pole

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

A force that can act at a distance is called

• non contact force

• friction

• balanced

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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

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

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