AC Power system gained much popularity because of

Question

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Option D: all of these

Explanation & Concepts:
The AC power system's dominance is attributed to the synergistic development of enabling technologies that solved fundamental transmission and conversion challenges. Transformers allowed for efficient voltage transformation ($V_2 = V_1 \frac{N_2}{N_1}$) for long-distance transmission, polyphase circuits enabled efficient power delivery and rotating magnetic fields, and induction motors provided robust, maintenance-free conversion of electrical energy into mechanical work.

Working Principle: The principle relies on the ability to step up voltage using transformers to reduce $I^2R$ losses during transmission, and step it down for safe consumer usage. Polyphase (three-phase) systems create a constant magnitude rotating magnetic field in induction motors, ensuring smooth torque and self-starting capability without the need for brushes or commutators.

Key Formulas: $P = \sqrt{3} V_L I_L \cos \phi$ — Total power in a balanced 3-phase AC system; $V_s = V_p \frac{N_s}{N_p}$ — Transformer voltage transformation ratio

Key Points: Transformers enable high-voltage transmission, reducing current and line losses ($P_{loss} \propto I^2$).; Polyphase circuits provide constant instantaneous power, reducing vibrations in electrical machinery.; Induction motors are mechanically simple, rugged, and cheaper than DC motors.; Rotating magnetic fields are naturally generated by polyphase AC supplies.

Advantages: High efficiency via voltage transformation; Simple and reliable induction motor construction; Easier fault protection and circuit interruption; Constant torque production in polyphase systems

Disadvantages: Skin effect increases conductor resistance at higher frequencies; Reactive power requirements (VAr) complicate voltage control

Applications: National Power Grids; Industrial motor drives; Domestic power distribution

Additional Info: The 'War of Currents' between Tesla/Westinghouse (AC) and Edison (DC) was largely decided by the economic advantage of transformers in long-distance power distribution.. Option A, B, and C are all essential components that allowed the AC system to outperform contemporary DC distribution networks.

Answer: D is correct — The widespread adoption of AC power was driven by the cumulative technological breakthroughs of the transformer, polyphase circuits, and the induction motor.

Exam Tip: Always relate power system efficiency to the relationship $P=VI$; raising voltage is the primary method to minimize current and transmission losses.

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Option A: transformers invetion

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Option B: poly phase circuits invention

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Option C: induction motor invention

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