Question 1: Define the National Grid and explain its purpose in supplying electricity.

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

Question 2: What is the typical voltage level transmitted through the high-voltage transmission lines in the UK National Grid?

Answer: Around 400,000 volts (400 kV).

Question 3: Explain why high voltage is used for long-distance transmission of electricity in the National Grid.

Answer: High voltage reduces the current for a given power, which in turn decreases resistive losses in the transmission lines, making long-distance transmission more efficient.

Question 1: A transmission line carries a current of 500 A at a voltage of 400 kV. Calculate the power transmitted through the line in megawatts (MW). Use the formula Power (P) = Voltage (V) × Current (I).

Answer: 200 MW

Question 2: If the resistance of a segment of a transmission line is 0.05 ohms and the current is 500 A, calculate the power loss due to resistance in watts. Use the formula Power loss = I² × R.

Answer: 12500 W

Question 1: Describe three safety precautions that engineers must take when working on high-voltage transmission lines.

Answer: Wearing insulating gear, ensuring power is switched off before maintenance, and maintaining a safe distance from live conductors.

Question 2: Identify two variables that engineers might need to control during the construction of high-voltage transmission lines.

Answer: Voltage levels and tension in the cables.

Question 1: A forensic investigator finds a burnt electrical appliance that was connected to a domestic socket. Using measurements of the appliance's resistance (10 ohms) and the voltage supplied (230 V), calculate the current flowing through the appliance. What might this suggest about the cause of the fire?

Answer: 23 A; The high current could indicate a short circuit or overload, which may have caused the fire.

Question 2: Explain how forensic investigators can use electrical measurements to help identify faults or crimes involving electrical devices.

Answer: By measuring resistance, current, and voltage in electrical devices, investigators can determine if faults such as short circuits, overloads, or improper wiring occurred. These measurements can help establish whether electrical failure was accidental or intentional, aiding in crime scene analysis.

Question 1: Discuss the importance of the National Grid in maintaining a reliable electricity supply for homes and industries. Include in your answer how the grid's design helps prevent blackouts and manage demand.

Answer: The National Grid is vital for distributing electricity efficiently across the country, ensuring homes and industries receive a continuous supply. Its high-voltage transmission lines reduce energy loss over long distances. The grid includes substations and transformers that step voltage levels up or down, allowing control over power flow. This design helps prevent blackouts by balancing supply and demand, and by isolating faults to prevent widespread outages. The grid's real-time monitoring and control systems further enhance reliability and stability.