# Homework Help: Magnetic field of a lightning bolt

1. Oct 12, 2004

### 1timeuse

In a lightning bolt, 14 C of charge flows in a time of 1.5 x 10^-3 s. Assuming that the lightning bolt can be represented as a long, straight line of current, what is the magnitude of the magnetic field at a distance of 27 m from the bolt?

do i use 27 m as the radius in the equation

$$B = \frac {\mu I}{2\pi r}$$

Last edited: Oct 12, 2004
2. Oct 13, 2004

### Tide

Yes! That's just Ampere's law applied to a cylindrically symmetric current.