Example from Physics, 19.1 Ohm's law

Current in a Lightning Strike

A lightning strike can transfer as many as $10^{20}$ electrons from the cloud to the ground. If the strike lasts 2 ms, what is the average electric current in the lightning?

Work it out on paper first. Then open the solution one step at a time, and stop as soon as you can finish on your own.

Strategy
Use the definition of current, $I = \frac{Δ Q}{Δ t}$ . The charge $Δ Q$ from $10^{20}$ electrons is $Δ Q = n e$ , where $n = 10^{20}$ is the number of electrons and $e = - 1.60 \times 10^{- 19} C$ is the charge on the electron. This gives

$Δ Q = 10^{20} \times (−1.60 \times 10^{−19} C) = −16.0 C.$
19.2

The time $Δ t = 2 \times 10^{−3} s$ is the duration of the lightning strike.
Solution
The current in the lightning strike is

$\begin{matrix} I & = & \frac{Δ Q}{Δ t} \\ = & \frac{−16.0 C}{2 \times 10^{−3} s} \\ = & −8 kA. \end{matrix}$
19.3

0 of 2 steps open

How did it go?

Strategy

Solution

Strategy

Solution