Electricity & Noncontact Forces Unit Test

Renaldo and Nasreen build an electromagnet by wrapping a wire around a nail and connecting the wire to both terminals of a battery. When they test the electromagnet, it can pick up 6 paper clips. Their teacher wants all groups to pick up at least 10 paper clips. What revisions could Renaldo and Nasreen make to increase the number of paper clips their electromagnet picks up?

• make the wire longer

• remove the nail from the center of the wire

• increase the number of loops of wire around the nail

• spread the loops of wire apart on the nail so they do not touch

In an electric motor, at the moment that the half-turn of the rotor (central electromagnet) completes, the field of this electromagnet

• stops

• flips

• turns off

• increases

Donna is attempting to make an electromagnet to pick up old nails in and around her driveway. Which of these materials would be best to use for the core in order to make the strongest electromagnet to pick up the most nails?

• Use a nail with a galvanized coating

• Wrap more turns of wire around the nail

• water

Which electromagnet would have the most strength?

• An electromagnet with 20 coils

• iron nail

• wooden stake

• plastic tube

• An electromagnet with 5 coils

Which change would result in a stronger electromagnet?

• Reducing the number of batteries

• Increasing the voltage of the battery

• Substituting another metal for the iron core

• Decreasing the number of coils around the iron core

Which statement about magnetic poles is accurate?

• Same magnetic poles attract, while different magnetic poles repel

• Opposite magnetic poles attract, while like magnetic poles repel

• Opposite magnetic poles repel, while like magnetic poles attract

Sal and Marie were experimenting with bar magnets in science class, picking up chains of paper clips. Where should they expect the magnetic force of the bar magnet to be the strongest and pick up the most paper clips?

• at both Poles

• at the South Pole

• at the North Pole

• in the center of the bar magnet

How would a bar magnet orient itself relative to this planet's magnetic field?

• N

• S

Coiling wire around an iron core and applying an electric current through the wire creates a temporary magnet called an electromagnet. What would increase the strength of an electromagnet?

• Use a smaller nail.

• Use a battery with less voltage.

• Use a battery with more voltage.

• Use fewer coils of wire around the nail.

Ms.Poole's class is studying magnets. Ms. Poole showed her students how to make an electromagnet using a nail, a D-cell battery, and plastic coated wire. The students wrapped the wire around the nail and then attached the ends to the battery. When they were finished, they tested their magnets by trying to see how many paperclips their magnets could pick up. They also tested whether they could increase the strength of their electromagnets by using more coils of wire. They recorded the class average of their results in the data table seen here. Review the students' data. Predict how many paper clips the students would pick up if they used 50 coils of wire around bigger nails.

• 25

• 50

• 100

• 250