Electromagnets
Electromagnets produce a magnetic field from an electrical current. Electromagnets can be found in the motors of everyday devices including cars, washing machines, refrigerators, and computers. The number of wire coils, type of nail, and voltage of the battery are a few factors that affect the strength of the magnetic field.
A group of students plans several investigations to test the factors affecting an electromagnetic field. First, they vary the number of times an insulated wire is wrapped around a steel nail. The ends of the wire are attached to each end of a 1.5 V battery to complete a simple circuit, as shown in the image.
The students record the maximum number of paper clips the magnet will lift for each trial.
Number of Coils Number of Paper Clips
10 3
20 7
30 9
40 12
Next, the students add a second battery and repeat the investigation.
They record the maximum number of paper clips the magnet will lift for each trial.
Number of Coils Number of Paper Clips
10 5
20 8
30 11
40 16
Then, they wrap insulated wire 25 times around different types of nails. The ends of the wire are attached to a single battery. The students record the properties of each type of nail and the maximum number of paper clips the magnet will lift for each trial.
Metal
Electrical Conductivity
Magnetic
(Yes/No)
Number of Paper Clips
Aluminum High conductivity No 0
Iron Medium conductivity Yes 15
Steel Low conductivity Yes 10
Multiple Choice Question
Students conduct another investigation using insulated wire and a steel nail. They increase the number of coils to 50 and add a third battery. Which best describes what happens to the magnetic field?
A.
The magnetic field becomes weaker, decreasing the number of paper clips.
B.
The magnetic field becomes stronger, increasing the number of paper clips.
C.
The increase in coils and battery cancels each other out, resulting in no magnetic field.
D.
The increase in coils interferes with the third battery, resulting in a weaker magnetic field.
1 answer
The correct answer is:
B. The magnetic field becomes stronger, increasing the number of paper clips.
This conclusion is based on the understanding that both an increase in the number of coils wrapped around the nail and an increase in the voltage supplied by adding batteries contribute to strengthening the magnetic field of the electromagnet. Therefore, increasing the coils to 50 and adding a third battery would result in a stronger magnetic field, allowing the magnet to lift more paper clips.
