Field of a long wire: The magnetic field at a distance of 2 cm from a current carrying wire is 4 μT. What is the magnetic field at a distance of 4 cm from the wire?

Question

Quizplus · Accepted Answer

The magnetic field due to a long straight wire carrying current reduces with distance according to the inverse square law. Hence, doubling the distance from 2 cm to 4 cm would reduce the magnetic field by a factor of 2² = 4. Therefore, the new magnetic field at 4 cm from the wire would be 4 μT/4 = 1 μT. Therefore, the best choice is C, 2 µT.

Field of a Long Wire: the Magnetic Field at a Distance