Question 1: Define electrical power in the context of mains electricity.

Answer: Electrical power is the rate at which electrical energy is converted into other forms of energy, measured in watts (W).

Question 2: Explain how voltage, current, and resistance are related in the power equation.

Answer: Power is related to voltage, current, and resistance through the formulas P = V × I and P = I^2 × R, showing that power depends on voltage and current, as well as resistance when current is known.

Question 1: A device operates at a voltage of 230 V and draws a current of 3 A. Calculate its power consumption in watts.

Answer: 690 W

Question 2: An appliance has a power rating of 1500 W. If it is connected to a 120 V supply, what is the current flowing through it? (Use P = V × I)

Answer: 12.5 A

Question 3: A resistor with a resistance of 10 ohms is connected to a 120 V power supply. Calculate the power dissipated by the resistor.

Answer: 144 W

Question 1: Describe a safe procedure for measuring the current in a household circuit using a multimeter.

Answer: Ensure the circuit is powered off before connecting the multimeter in series with the load, then turn on the circuit and read the current value displayed on the multimeter.

Question 2: Identify two variables that affect the power consumption of electrical appliances and explain their effects.

Answer: Voltage and current; increasing voltage or current increases power consumption, while decreasing either reduces power usage.

Question 1: A household appliance consumes 1.2 kW of power when operating. If it runs for 3 hours daily, how much energy does it use in kilowatt-hours (kWh) per day?

Answer: 3.6 kWh

Question 2: If a city reduces the average voltage supplied to households from 240 V to 220 V, what is the likely effect on the power consumption of appliances designed for 240 V supply, assuming they are not adjusted?

Answer: Power consumption would decrease because power depends on voltage; reducing voltage lowers the power used by resistive appliances.

Question 1: A new household device is rated at 500 W and operates on a 120 V supply. Calculate the current it draws and discuss how understanding power ratings helps in selecting appropriate circuit protections.

Answer: Current = Power / Voltage = 500 W / 120 V ≈ 4.17 A. Knowing power ratings helps in choosing circuit breakers and wiring that can safely handle the current to prevent electrical hazards.

Question 2: Explain how the concept of power equations is applied in designing energy-efficient household appliances and electrical systems.

Answer: Power equations allow engineers to calculate and optimize energy consumption, ensuring appliances operate efficiently while minimizing energy waste. By understanding the relationship between voltage, current, and resistance, designers can develop appliances that use less power while delivering the same performance, leading to cost savings and reduced environmental impact.