Question

A vertical electric wire in the wall of a building carries a dc current of 20 a upward. What is the magnitude of the magnet field at a point 0.1 m due north of this wire? Answer in units of μt.

Answer 1

B = μI / 2(π)r 
= (4π×10^−7 Tm/A)(20A) / 2π(0.1m) 
= (2x10^-7 Tm/A)(20A) / (0.1m) 
= 4x10^-5T 
= 40 µT


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