Question 1: Define electrical resistance and explain its role in an electric circuit.

Answer: Electrical resistance is a measure of how much a material opposes the flow of electric current. It determines how much current flows for a given voltage, affecting the power consumption and heat produced in the circuit.

Question 2: Describe how the resistance of a wire changes if its length increases while keeping its material and thickness constant.

Answer: The resistance increases proportionally with the length of the wire because longer wires offer more opposition to the flow of current.

Question 3: Which material generally has the lowest resistance: copper, rubber, or glass? Explain your answer.

Answer: Copper has the lowest resistance because it is a good conductor, whereas rubber and glass are insulators with very high resistance.

Question 4: Using Ohm's Law (V = IR), calculate the resistance of a circuit where a voltage of 12 V causes a current of 3 A to flow.

Answer: Resistance R = V / I = 12 V / 3 A = 4 ohms

Question 5: In a practical experiment, what variables would you change to investigate how resistance varies with material? List at least two.

Answer: Variables include the type of material (e.g., copper, aluminium), and the length or thickness of the wire.

Question 6: Identify two safety precautions to observe when handling electrical circuits during practical investigations of resistance.

Answer: Ensure the circuit is disconnected before changing components and avoid touching live wires to prevent electric shocks.

Question 7: State why a resistor is used in electronic devices and how it relates to resistance.

Answer: Resistors are used to control current flow and voltage distribution within circuits, directly relating to their resistance value.

Question 8: A wire has a resistance of 2 ohms and carries a current of 0.5 A. What is the voltage across the wire?

Answer: V = IR = 2 ohms * 0.5 A = 1 volt

Question 9: Explain how resistance impacts the efficiency of electrical power transmission over long distances.

Answer: Higher resistance in transmission lines causes more energy to be lost as heat, reducing efficiency. Using conductors with low resistance and increasing voltage helps minimise these losses.

Question 10: Identify a modern technological application that relies on controlling resistance and briefly describe its purpose.

Answer: Thermistors in temperature sensors control resistance to measure temperature changes accurately in electronic devices.

Question 11: Describe how resistance plays a role in the operation of a light-emitting diode (LED).

Answer: Resistors limit the current flowing through the LED to prevent damage and ensure proper operation by controlling resistance in the circuit.