11.2 Power Generation & Transmission

Which of the following best describes the principle of a transformer?

A. Conversion of mechanical energy to electrical energy

B. Conversion of direct current (DC) to alternating current (AC)

C. Transfer of electrical energy between two or more circuits through electromagnetic induction

D. Conversion of high voltage to low current

A transformer has a primary coil with 100 turns and a secondary coil with 500 turns. If the primary coil is connected to a 230 V supply, what is the voltage across the secondary coil?

A. 46 V

B. 1150 V

C. 500 V

D. 230 V

Which type of transformer is used to increase the voltage and decrease the current?

A. Isolation transformer

B. Step-down transformer

C. Step-up transformer

D. Power transformer

Why was direct current (DC) initially preferred over alternating current (AC) for power transmission?

A. AC was more dangerous than DC

B. DC could be transmitted over longer distances without significant loss

C. AC transformers were not yet invented

D. DC generators were more efficient than AC generators

Which of the following is NOT an advantage of using alternating current (AC) over direct current (DC) for power transmission?

A. AC can be easily transformed to different voltages

B. AC systems are simpler and cheaper

C. AC can be transmitted over long distances with minimal loss

D. AC is safer for household use

a) Explain the principle of magnetic induction in the context of transformers. How does it enable the transformation of voltages? [3]

b) A transformer has a primary coil with 500 turns and a secondary coil with 1500 turns. If the voltage applied to the primary coil is 230 V, what is the voltage across the secondary coil? [2]

a) Differentiate between step-up and step-down transformers in terms of their coil turn ratios and their effect on voltage. [3]

b) Why is high voltage transmission used in power grids? [2]

a) Describe the main advantages and disadvantages of AC transmission over DC transmission. [3]

b) In the context of power distribution, explain the role and importance of substations. [2]

a) Describe the role of dielectrics in the construction of capacitors and how they influence the capacitance. [3]

b) A transformer is designed to step down a voltage from 240 V to 120 V. If the primary coil has 600 turns, how many turns should the secondary coil have? [2]

c) What is the significance of flux linkage in the context of Faraday's Law? [2]

a) Explain the difference between AC and DC transmission in terms of their historical context. [3]

b) How does a step-up transformer differ from an isolation transformer in terms of their applications? [2]

c) Why are eddy currents considered undesirable in transformers, and how are they minimised? [3]