Question 16.2: Turbulent motions in thunderstorms cause charge separations ...
Turbulent motions in thunderstorms cause charge separations that result in a potential difference of around 10 MV between cloud and ground. When lightning occurs, it transfers some 50 C of charge between cloud and ground. How much energy is released in the lightning strike?
ORGANIZE AND PLAN Potential difference is the potential energy difference per unit charge. Equation 16.4b relates potential energy difference and potential difference: \Delta U=q_{0} \Delta V . \text { Here } q_{0} is the 50-C charge and ΔV is the 10-MV potential difference between cloud and ground (Figure 16.4).
\Delta U=q_{0} \Delta V (Potential energy difference; SI unit: J) (16.4b).
The charge’s potential energy drops as it falls through the 10-MV potential difference, so ΔU is the energy released:
\text { Energy released }=\Delta U=q_{0} \Delta V=(50 C )(10 MV )=500 MJ.
REFLECT That’s a lot of energy. You don’t want to be on the receiving end of a lightning strike! In what forms do you notice this energy being released?