The magnetic field 0.02 m from a wire is 0.1 T. What is the magnitude of the magnetic field 0.01 m from the same wire?

For a straight wire, the magnetic field is inversely proportional to the distance from the wire. The distance decreases from 0.02 m to 0.01 m, which is half as far away, so the field doubles: 0.1 T × 2 = 0.2 T. Therefore, the correct choice is 0.2 T.

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