A lightning strike delivers $I = 30 kA$ and transfers $Q = 15 C$ of charge
Charge & Current - OCR A-Level Physics
- A lightning strike delivers $I = 30$ kA and transfers $Q = 15$ C of chargeA property of matter that causes it to experience a force in an electromagnetic field. Measured in coulombs (C)..
- Find the time the strike lasts and the number of electrons transferred.
$$\begin{aligned}
\Delta t &= \frac{\Delta Q}{I} \\
&= \frac{15}{30 \times 10^{3}} \\
&= 5.0 \times 10^{-4} \text{ s}
\end{aligned}$$
$$\begin{aligned}
n &= \frac{Q}{e} \\
&= \frac{15}{1.6 \times 10^{-19}} \\
&= 9.4 \times 10^{19} \text{ electrons}
\end{aligned}$$
Examiner Tips and Tricks
- Always convert kA to A (multiply by $10^{3}$) before substituting.
- Check your answer makes physical sense: a lightning strike is extremely fast (fraction of a millisecond) with a huge number of electrons.