Answer to Question #181363 in Electricity and Magnetism for Diem

Question

A thunderbolt is made of an amount of charge travelling from clouds (at a given potential V1) to ground (at a given potential V2). We can think about it as a wire through which a certain amount of intensity current travels. In order to give an estimation of the amount of charge travelling in the thunderbolt, we measure the intensity of the magnetic field 150m apart from the thunderbolt. The value of B resulted to be 2.5 · 10−4T .

Determine the intensity of electrical current.

Answer 1

The magnitude of the field at a certain distance d from the wire can be expressed as

$$B=\frac{\mu_0 I}{2\pi d},\\\space\\ I=\frac{2\pi dB}{\mu_0}=187500\text{ A}.$$