Question 1: Define an electromagnet and explain how it differs from a permanent magnet.

Answer: An electromagnet is a magnet created by passing an electric current through a coil of wire, producing a magnetic field. Unlike a permanent magnet, its magnetic field can be switched on and off by controlling the current.

Question 2: Describe the role of the core material in an electromagnet and name a common material used.

Answer: The core material enhances the magnetic field produced by the coil. A common core material is soft iron, which is easily magnetised and demagnetised.

Question 1: Calculate the magnetic field strength (B) at the centre of a solenoid with 200 turns, a length of 0.5 m, and a current of 3 A. Use the formula B = μ₀ * (N/L) * I, where μ₀ = 4π × 10⁻⁷ T·m/A.

Answer: B = 4π × 10⁻⁷ * (200 / 0.5) * 3 = approximately 3.02 × 10⁻³ Tesla.

Question 2: An automotive electromagnet has a coil with 1500 turns and carries a current of 2 A. If the magnetic flux density (B) needed to operate a relay is 0.05 Tesla, what is the required length of the solenoid? Assume μ₀ = 4π × 10⁻⁷ T·m/A.

Answer: L = μ₀ * N * I / B = (4π × 10⁻⁷) * 1500 * 2 / 0.05 ≈ 0.0754 meters.

Question 1: Outline a simple experiment to demonstrate how increasing the current in an electromagnet affects its magnetic strength. Include variables to control and safety precautions.

Answer: An experiment can be set up with a solenoid coil, a power supply, and a magnetic compass or iron filings. Vary the current using a resistor or variable power supply while keeping the number of turns and core material constant. Measure the magnetic strength via the deflection of the compass or the density of filings. Safety precautions include ensuring proper insulation, not exceeding the current rating, and avoiding overheating of the coil.

Question 1: A vehicle uses an electromagnet with a coil of 2500 turns and a current of 4 A to operate a locking mechanism. The magnetic flux density inside the core is measured at 0.08 Tesla. If the number of turns is increased to 3000 while keeping the current the same, what will be the new flux density? Assume magnetic properties remain constant.

Answer: Since B ∝ N * I, increasing N from 2500 to 3000 increases B proportionally: B_new = 0.08 * (3000 / 2500) = 0.096 Tesla.

Question 1: Explain how electromagnets are used in automotive starter motors. Include the principle behind their operation and why they are preferred over permanent magnets in this context.

Answer: In automotive starter motors, electromagnets are used to engage the gear with the engine's flywheel. When the ignition is turned, current flows through the electromagnet's coil, creating a magnetic field that pulls the starter gear into contact with the flywheel. This allows the motor to turn the engine over. Electromagnets are preferred because their magnetic field can be switched on or off, enabling controlled engagement, and they can generate stronger magnetic forces as needed.

Question 2: Identify two safety precautions that must be taken when working with electromagnets in automotive repair settings.

Answer: Ensure the electromagnet is properly insulated to prevent electric shocks, and avoid overheating the coil by controlling current and allowing cooling periods to prevent burns or damage.