Question 1: Define the term 'National Grid' and explain its purpose in supplying electricity across the UK.

Answer: The National Grid is a network of high-voltage power lines and substations that transmit electricity from power stations to homes and businesses across the UK, ensuring efficient and reliable supply.

Question 2: Describe the main components involved in the transmission of electricity in the National Grid.

Answer: Key components include power stations, high-voltage transmission lines, substations, step-down transformers, and distribution lines to homes and industries.

Question 1: Calculate the current drawn by a domestic appliance rated at 2400 W when connected to a 230 V supply. (Use P = V × I)

Answer: I = P / V = 2400 W / 230 V ≈ 10.43 A

Question 2: A household consumes 900 kWh of electricity in a month. If the cost of electricity is £0.15 per kWh, what is the total cost for that month?

Answer: Cost = 900 kWh × £0.15 = £135

Question 3: A transmission line operates at 400 kV. If the power transmitted is 1 GW, calculate the current in the line. (Use P = V × I)

Answer: I = P / V = 1,000,000,000 W / 400,000 V = 2500 A

Question 1: Identify three safety precautions that must be observed when working near high-voltage transmission lines.

Answer: Maintain safe distance, wear appropriate protective equipment, and ensure power is switched off before maintenance.

Question 2: Explain why step-up transformers are used at power stations and step-down transformers are used near consumers.

Answer: Step-up transformers increase voltage for efficient long-distance transmission, reducing energy loss; step-down transformers decrease voltage to safe levels for domestic use.

Question 1: A city consumes an average of 50 MW of electricity during peak hours. If the transmission line operates at 400 kV, what is the approximate current in the line? (Use P = V × I)

Answer: I = P / V = 50,000,000 W / 400,000 V = 125 A

Question 2: If the efficiency of transmitting electricity through the grid is 95%, how much power must be generated at the power station to supply 50 MW to the city?

Answer: Power generated = Power supplied / efficiency = 50 MW / 0.95 ≈ 52.63 MW

Question 1: Explain how the use of high-voltage transmission lines reduces energy loss during long-distance transmission of electricity. Include relevant formulas in your explanation. (6 marks)

Answer: High-voltage transmission lines reduce energy loss because power loss is proportional to I²R, where I is current and R is resistance. By increasing the voltage (V) and decreasing current (I) using step-up transformers, the power transmitted remains the same, but the current decreases. Since power loss P_loss = I²R, reducing I significantly reduces energy loss during transmission. Therefore, the use of high voltage in the grid improves efficiency and reduces the amount of energy lost as heat.

Question 1: Describe how the National Grid supports renewable energy sources such as wind and solar farms.

Answer: The National Grid connects renewable energy sources like wind and solar farms to the main supply network, allowing the electricity generated from these sources to be transmitted over long distances to consumers across the country.

Question 2: Discuss the challenges faced by the National Grid in integrating increasing levels of renewable energy into the electricity supply.

Answer: Challenges include managing variable and unpredictable energy output, maintaining grid stability, upgrading infrastructure to handle new sources, and ensuring consistent supply during periods of low renewable generation.