Question

A typical current in a lightning bolt is 104 A. Estimate the magnetic field 9 m from the bolt (in T).

Answer 1

The magnetic field at a distance r from a straight wire (which is an okay approximation of a lightning bolt) is given by:

`B=(\mu_0 I)/(2\pi r)`

where
`\mu_0` is the magnetic constant
`\mu_0 =4\pi*10^(-7)\frac{\text{H}}{\text{m}}`

and I is the current.

So, when you plug everything into the equation you get:

`B=(\mu_0 I)/(2\pi r)=((4\pi*10^(-7))(104))/((2\pi)(9))\approx 2.3* 10^(-6) \text{T}`