CAIE IGCSE Physics 4.2.3.7 P D V W Q Questions

Practise using V = W/Q to connect potential difference, energy transfer and charge, including unit equivalence and multi-step lightning or circuit calculations.

Exam points

Use and rearrange V = W/Q to calculate p.d., energy or charge, recognise one volt as one joule per coulomb, and convert megajoules and other prefixes before substitution.

[Maximum number: 2]

Fig. 7.1 shows two charged metal plates. X marks the position of the centre of the space between the plates.

Fig. 7.1

During a thunderstorm, an electric field is set up between a cloud and the ground. Charges on the cloud and on the ground are shown in Fig. 7.2.

Fig. 7.2

The lightning shown in Fig. 7.2 discharges a current of 28000 A for 0.0012 s .

The lightning transfers $1.2 \times 10^{8} \mathrm{~J}$ of energy.

Calculate the potential difference between the base of the cloud and the ground.
potential difference =
[Total: 7]

(p.d. =) 3.6 MV OR $3.6 \times 10^{6} \mathrm{~V}$
E=I t V OR(V=) E / It $\mathbf{OR}(V=) E / Q \mathbf{OR}(V=) 1.2 \times 10^{8} / 34$

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CAIE IGCSE Physics 4.2.3.7 P D V W Q Questions question 1