Question 1: Define a transformer and explain its primary function in electrical systems.

Answer: A transformer is an electrical device that changes the voltage of alternating current using electromagnetic induction, primarily to increase (step-up) or decrease (step-down) voltage levels in power transmission.

Question 2: Describe the role of the core in a transformer and why it is usually made of iron or aluminum.

Answer: The core provides a path for magnetic flux, increasing efficiency by reducing energy loss. Iron is used because it has high magnetic permeability, enhancing magnetic flux, while aluminum is used in some cases for weight and cost considerations.

Question 3: Explain the principle of electromagnetic induction that allows transformers to operate.

Answer: Transformers operate on the principle of electromagnetic induction, where a changing magnetic flux in the core induces an electromotive force (voltage) in the secondary coil when an alternating current flows through the primary coil.

Question 1: A transformer has 500 turns in the primary coil and 50 turns in the secondary coil. If the primary voltage is 240 V, what is the voltage in the secondary coil? (Use the transformer voltage ratio formula: Vs/Vp = Ns/Np)

Answer: Vs = (Ns/Np) * Vp = (50/500) * 240 V = 0.1 * 240 V = 24 V

Question 2: A transformer steps down voltage from 11000 V to 220 V. If the primary current is 50 A, what is the current in the secondary coil, assuming ideal conditions? (Use the current ratio formula: Is/Ip = Np/Ns)

Answer: Is = (Np/Ns) * Ip = (11000/220) * 50 A = 50 * 50 A = 2500 A

Question 1: List three safety precautions that should be observed when working with high-voltage transformers.

Answer: Ensure proper insulation, avoid contact with live parts, and use appropriate protective gear to prevent electric shocks or accidents.

Question 2: Describe a simple experiment to demonstrate the operation of a transformer using a low-voltage AC supply and a soft iron core.

Answer: Use a primary coil connected to an AC power source, wrap it around a soft iron core, and then connect a secondary coil nearby. When the AC supply is turned on, an induced voltage appears in the secondary coil, demonstrating electromagnetic induction. Students should note safety precautions such as keeping connections insulated and handling equipment carefully.

Question 1: A power plant uses a step-up transformer to increase voltage from 25,000 V to 400,000 V for long-distance transmission. If the primary current is 200 A, what is the secondary current assuming no energy loss? Explain your reasoning.

Answer: Using conservation of power: Power in primary = Power in secondary, so Vp * Ip = Vs * Is. Therefore, Is = (Vp * Ip) / Vs = (25,000 V * 200 A) / 400,000 V = 5,000,000 VA / 400,000 V = 12.5 A.

Question 1: Explain why transformers are critical in reducing power loss during electricity transmission over long distances.

Answer: Transformers step up the voltage for transmission, which reduces current and consequently minimizes resistive power losses in the transmission lines, making long-distance electricity delivery more efficient.

Question 2: Identify an everyday device that uses a transformer and describe its purpose.

Answer: A mobile phone charger uses a transformer to convert high-voltage AC from the mains to low-voltage AC suitable for charging the phone's battery.