Electricity and Magnetism 3

The magnetic field of an electromagnet can be increased by 

• changing the direction of the current.
• decreasing the current.
• increasing the number of coils. 
• decreasing the number of coils. 

What does this illustration represent? 

• magnetic material that is not magnetized
• magnetic material that is magnetized
• non-magnetic material
• arrangements of atoms in a domain

In this illustration, the magnetic field is strongest ___. 

• near either pole
• near the north pole
• near the south pole
• halfway between the poles

What effect does increasing the current flowing in the wire have on an electromagnet?

• It decreases the strength of the magnetic field. 
• It increases the strength of the magnetic field. 
• It has no effect on the electromagnet. 
• It causes it to become a permanent magnet. 

You observe that magnets A and B are attracted to each other and "stick." Which sentence BEST explains this observation? 

• Both are positively charged. 
• Both are tightly bonded to each other. 
• Both are composed of smaller, individual magnets. 
• Both have all their magnetic domains aligned in the same direction. 

As electrons flow through the metal wire in the center of this motor, the metal begins to turn. This is because

• electric charges act as tiny magnets. 
• a flow of electrons experiences a force in a magnetic field. 
• positive electric charges are attracted to the south pole of a magnet. 
• positive electric charges are attracted to the north pole of a magnet. 

Objects that keep their magnetic properties for a long time are called ___. 

• electromagnets
• magnetic domains
• permanent magnets
• temporary magnets

A coil of wire with a current is called a(n)

• insulator.
• solenoid. 
• electromagnet.
• galvanometer.

The function of an electric motor is to change ___. 

• chemical energy to electrical energy
• electrical energy to chemical energy
• electrical energy to mechanical energy
• mechanical energy to electrical energy

A coil of wire that has a soft iron core and that acts as a magnet when an electric current is in the coil called a(n) 

• ferromagnet.
• electromagnet. 
• permanent magnet.
• temporary magnet.