Question 1: In mains electricity, power is the rate at which electrical energy is transferred or converted. It is calculated using the voltage and current in the circuit. The basic power equation is P = VI, where P is power in watts (W), V is voltage in volts (V), and I is current in amperes (A).

Answer: Power (P) in watts equals voltage (V) in volts times current (I) in amperes, expressed as P = VI.

Question 2: Define electrical power in the context of mains electricity.

Answer: Electrical power is the rate at which electrical energy is transferred or used in a circuit, measured in watts (W).

Question 3: Which of the following options correctly represents the relationship between power (P), voltage (V), and current (I)?

Answer: P = V x I

Question 4: Fill in the blank: The power dissipated in a resistor can also be calculated using the formula P = I^2 R, where R is resistance in ohms (Ω).

Answer: P = I^2 R

Question 5: Explain why understanding power equations is important for designing electrical appliances.

Answer: Understanding power equations allows engineers to determine how much energy an appliance will consume, ensuring safety, efficiency, and appropriate power ratings are selected to prevent overloads and optimise performance.

Question 6: Calculate the power used by a heater that operates at 230 V and draws a current of 10 A.

Answer: P = V x I = 230 V x 10 A = 2300 W

Question 7: A wire has a resistance of 5 Ω and carries a current of 4 A. What is the power dissipated in the wire?

Answer: P = I^2 R = (4 A)^2 x 5 Ω = 16 x 5 = 80 W

Question 8: Identify three variables that affect the power consumption of an electrical device in a mains circuit.

Answer: Voltage (V), current (I), and resistance (R).

Question 9: Describe a simple experiment to measure the power consumption of a small appliance.

Answer: Use a multimeter or an appropriate power meter to measure the voltage and current drawn by the appliance while it is in operation. Calculate the power using P = VI. Ensure safety precautions like unplugging when connecting meters are observed.

Question 10: In a scenario where a device operates at 240 V and consumes 2 kW of power, what is the current drawn by the device?

Answer: I = P / V = 2000 W / 240 V ≈ 8.33 A

Question 11: Discuss how understanding power equations can help in reducing energy wastage in household electrical systems.

Answer: By understanding power equations, consumers and engineers can select energy-efficient appliances, avoid overloading circuits, and implement proper maintenance to ensure devices operate at optimal power levels. This reduces unnecessary energy consumption, lowers electricity bills, and minimises environmental impact.