Charge, Energy and Power

IGCSE Edexcel Physics
2.4-2.5, 2.14-2.21 Charge and Energy
Key Concepts: $Q = It$, $E = QV$, $P = IV$.

Section A: Charge

1. A current of $0.8\,A$ flows for 50 s. Calculate the charge. [2]
2. Define current as the rate of flow of charge. [2]

Section B: Energy and Power

3. A charge of $2\,C$ passes through a $6\,V$ component. Calculate energy transferred. [2]
4. A device uses $I = 3\,A$ at $V = 10\,V$. Calculate power. [2]
5. The device in Question 4 runs for 120 s. Calculate energy transferred. [3]
6. A charger transfers 1800 C of charge at 5 V. Calculate the energy transferred. [2]
7. A 60 W lamp runs for 30 s on a 12 V supply. Calculate the charge that flows. [2]
Total marks: 15

Mark Scheme

1. $Q = It = 0.8 \times 50 = 40\,C$ [2]
2. Current is charge per unit time [2]
3. $E = QV = 2 \times 6 = 12\,J$ [2]
4. $P = IV = 3 \times 10 = 30\,W$ [2]
5. $E = IVt = 30 \times 120 = 3600\,J$ [3]
6. $E = QV = 1800 \times 5 = 9000\,J$ [2]
7. $P = IV \Rightarrow I = 60/12 = 5\,A$; $Q = It = 5 \times 30 = 150\,C$ [2]