Question 1: Define the motor effect and explain how it is utilised in electric motors.

Answer: The motor effect is the force experienced by a current-carrying conductor in a magnetic field. In electric motors, this force causes rotation by interacting with magnetic fields, converting electrical energy into mechanical energy.

Question 2: Describe the main components of a simple electric motor and their functions.

Answer: A simple electric motor consists of a coil of wire (armature), a magnetic field (magnet or electromagnet), a commutator, and brushes. The coil experiences a force when current flows, causing it to rotate. The commutator reverses current direction to maintain continuous rotation.

Question 3: Explain why the magnetic field is essential in the operation of an electric motor.

Answer: The magnetic field interacts with the current in the coil, producing a force (Lorentz force) that causes the coil to rotate, enabling the motor to convert electrical energy into mechanical energy.

Question 1: Calculate the magnetic force on a 0.5 m length wire carrying a current of 3 A when placed in a magnetic field of 0.2 T, perpendicular to the wire. Use the formula: F = BIL sin θ. Assume θ = 90°.

Answer: F = 0.2 T × 3 A × 0.5 m × sin 90° = 0.2 × 3 × 0.5 × 1 = 0.3 N

Question 2: A motor's coil has a resistance of 2 Ω and is connected to a 12 V power supply. Calculate the current flowing through the coil.

Answer: I = V / R = 12 V / 2 Ω = 6 A

Question 1: Identify three variables that affect the efficiency of an electric motor.

Answer: Magnetic field strength, coil resistance, and friction within the moving parts.

Question 2: List two safety precautions engineers should consider when designing electric motors for industrial use.

Answer: Ensuring adequate insulation to prevent electric shocks and incorporating thermal protection to avoid overheating.

Question 1: A motor operates at 80% efficiency with an input power of 150 W. Calculate the output power and describe what this indicates about the motor’s performance.

Answer: Output power = Efficiency × Input power = 0.8 × 150 W = 120 W. This indicates the motor converts most of the electrical energy into useful mechanical work, with some lost as heat.

Question 2: In an industrial setting, a motor runs continuously for 8 hours, consuming 1.2 kWh of energy. If the motor’s efficiency is 75%, what is the approximate mechanical energy output? (Note: 1 kWh = 3.6 MJ)

Answer: Total energy input = 1.2 kWh = 1.2 × 3.6 MJ = 4.32 MJ. Mechanical output = 0.75 × 4.32 MJ = 3.24 MJ.

Question 1: Explain how the motor effect is used in electric vehicles to improve energy efficiency and performance. (6 marks)

Answer: Electric vehicles utilise the motor effect by converting electrical energy from batteries into mechanical energy via electric motors. The motor's magnetic field interacts with current-carrying conductors to produce rotational force, enabling propulsion. Advances such as regenerative braking capture energy during deceleration, improving efficiency. Precise control of current and magnetic fields allows for smooth acceleration and deceleration, reducing energy wastage and enhancing overall performance.

Question 1: Describe how electric motors are used in everyday household appliances and discuss the importance of understanding the motor effect in their design.

Answer: Electric motors are used in appliances like washing machines, fans, and vacuum cleaners to convert electrical energy into mechanical motion. Understanding the motor effect helps engineers design efficient, reliable, and safe motors by selecting appropriate magnetic fields, materials, and configurations to optimise performance and reduce energy consumption.

Question 2: Propose a basic experimental setup to demonstrate the motor effect using simple materials, explaining the purpose of each component (theory only).

Answer: The setup includes a straight wire connected to a battery (power source), placed within a magnetic field generated by a strong magnet. The wire is mounted on a stand allowing free movement. When current flows through the wire, the magnetic field exerts a force on it, causing movement. This demonstrates the motor effect. Components: wire (conducts current), battery (provides current), magnet (creates magnetic field), stand (supports wire). Variables include current strength, magnetic field strength, and wire length. Safety precautions involve ensuring proper insulation and avoiding short circuits.