Read the passage about the factors that affect the magnetism of electromagnets.
An electromagnet consists of an insulated copper wire wound around an iron core and connected to a source of electricity. The magnetism of electromagnets disappears when the electricity is turned off. A student performs two experiments to study the factors that affect the magnetism produced by an electromagnet.
Experiment 1
He prepares an electromagnet by wrapping ten coils of a wire around an iron nail. The wire is then connected to a 4.5-volt battery. Next, the electromagnet is placed close to evenly spread iron paper clips.
He records the number of paper clips that are attracted to the magnet in a table, repeating the activity with different numbers of coils around the nail.
Number of coils Number of paper clips attracted to the magnet
10 6
15 11
20 17
25 23
Experiment 2
In his second experiment, he repeats the same procedure he used in Experiment 1, except that this time he keeps the number of coils the same but changes the battery voltage. He records the number of paper clips attracted each time in a second table.
Battery Voltage (V) Number of paper clips attracted to the magnet
3.0 3
4.5 6
6.0 9
7.5 13
Which question can be answered based on the results of Experiment 2?
A.
How does the strength of an electromagnet vary when the voltage of the power source changes?
B.
How does the strength of an electromagnet vary when the number of paper clips changes?
C.
How does the voltage of an electromagnet vary when the strength of the paper clips changes?
D.
How does the voltage of an electromagnet vary when the number of coils of wire changes?