A thunder cloud is modelled as an ideal parallel plate capacitor with circular horizontal plates. The upper region is positive and the lower region is negative.
The model is based on the following data:
Take the permittivity of free space as ε0=8.85×10−12 F m−1\varepsilon_0 = 8.85 \times 10^{-12}\text{ F m}^{-1}ε0=8.85×10−12 F m−1.
State the direction of the electric field lines between the upper and lower regions of the cloud model.
Suggest why the actual electric field lines in a real cloud would differ from those of the ideal parallel plate capacitor model.
Calculate the potential difference (p.d.) VVV between the upper and lower regions.
Calculate the capacitance CCC of this model capacitor.
Calculate the magnitude of the charge QQQ on one of the plates of the capacitor.
Fork lightning is an electrical discharge that occurs between the bottom of a cloud and the surface of the Earth. Another cloud has a charge of 120 C120\text{ C}120 C and is at a height of 3.0 km3.0\text{ km}3.0 km. The surface of the Earth has an electrical potential of 0 V0\text{ V}0 V.
Assuming this cloud acts as a point charge, calculate the magnitude of the electrical potential VVV of this cloud relative to the Earth.
A fork lightning strike of duration 40 ms40\text{ ms}40 ms occurs. The cloud discharges at a constant rate and is completely uncharged after the strike. Calculate the number of electrons reaching the ground in 1.5 ms1.5\text{ ms}1.5 ms.
22 exam-style questions on OCR A A Level Physics Capacitors, covering Capacitors, Energy, and Charging and discharging capacitors. Each one has a worked solution and a mark scheme showing where the marks go.