SAT Subject Physics Practice Question 475: Answer and Explanation

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Question: 475


In the diagram above, two wires are aligned side by side. They are both hooked into different circuits in which the current is switched on to allow current to flow in each circuit. Which of the following statements is correct?

A. The two currents destructively interfere with each other.
B. The two currents constructively interfere with each other.
C. The two wires attract and move closer.
D. The two wires repel and move away.
E. The two wires remain still.

Correct Answer: C


The correct answer is (C). The two wires have a magnetic field around them caused by the current in the wires. The two fields are in opposition, which weakens them on the sides closest to each other. This allows the un-weakened field on the other (outside) of the wires to push the two wires together

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