Magnetism

Where is the area of greatest magnetic strength on a bar magnet located?

• at both poles

• at the north pole, only

• at the south pole, only

• at the bottom side of the magnet

Select three common objects that contain an electromagnet.

• computer

• flashlight

• remote control

• stereo

• television

Amira wants to create an electromagnet. Which method should she use?

• Amira should connect the negative end of a battery to its positive end.

• Amira should connect two fridge magnets together with opposite poles.

• Amira should wrap a wire around an iron nail and connect it to a battery.

• Amira should wrap a wire around a bar magnet and connect it to a paper clip.

A student is investigating with magnets. She holds six magnets the same distance away from a pile of paper clips and records how many paper clips are attracted to the magnet. The table shows her data.

Which argument is best supported by the student's data?

• A permanent magnet can be turned on and off.

• An electromagnet's field strength can be controlled.

• A permanent magnet always requires at least one source of electricity.

• An electromagnet's field strength is always more than a permanent magnet's.

Kim is using an electric current to produce a magnetic field. What will happen when she turns off the current?

• The strength of the magnetic field will increase.

• The poles of the magnetic field will reverse.

• The magnetic field will disappear.

• The strength of the magnetic field will decrease.

Which picture shows a device that uses an electromagnet?

• 
• 
• 
• 

Rory puts a large book between two magnets. The magnets do not attract each other through the book. Which is the most likely reason?

• The book is taking away the magnetic poles.

• The book is changing the direction of the magnetic fields.

• The book is acting like a magnet that repels the other magnets.

• The book is stopping the magnets from touching each other's magnetic fields

Which of these is true?

• Thick objects can keep magnets from attracting each other.

• Thin objects are best at blocking magnetic fields.

• Water stops magnets from attracting each other.

• Paper can stop a magnetic field.

Which of the following will most likely happen when a person tests the strength of an electromagnet by increasing the number of times he or she wraps a wire in coils around a metal nail?

• The number of metal coils will have no effect on the magnetic field of the electromagnet.

• The magnetic field of electromagnet will increase and then decrease as the number of coils increases.

• The electromagnet will be able to pick up more metal tacks as the number of coils increases.

• The electromagnet will pick fewer metal tacks as the number of coils increases.

Which statement about electricity and magnetism is NOT true?

• Electromagnets are permanent magnets.

• Electrical currents produce a magnetic field around a wire.

• Magnets can push away other objects.

• Coils of wire around an iron core can become electromagnets.