A very long straight current-carrying wire produces a $\vec { B }$ field of 20 mT at a distance d from the wire.To measure a field of 5 mT due to this wire,you would have to go to a distance from the wire of

Question

Quizplus · Accepted Answer

The magnetic field due to a long straight current-carrying wire decreases as the inverse of the distance from the wire. This means that if we want to reduce the field strength by a factor of 4 (from 20 mT to 5 mT), we need to quadruple the distance. Quadrupling the distance corresponds to multiplying it by 4, which gives us the answer of 4d. Therefore, choice C is the correct answer.

A Very Long Straight Current-Carrying Wire Produces A B⃗\vec { B }B

A Very Long Straight Current-Carrying Wire Produces A $\vec { B }$