In a transformer the energy is conveyed from primary to secondary

Question

Examoogle · Accepted Answer

By the flux

Explanation: In a transformer, electrical energy is transferred from the primary winding to the secondary winding through the medium of a time-varying magnetic flux. Since there is no electrical connection between the two windings, the energy transfer is purely inductive via the common magnetic core.

Working Principle: When an alternating voltage is applied to the primary winding, it creates a time-varying magnetic flux ($\Phi$) in the transformer core. According to Faraday's Law of Electromagnetic Induction, this alternating flux links with the secondary winding and induces an electromotive force (EMF) in it, thereby transferring energy.

Key Formulas: $e_2 = -N_2 \frac{d\Phi}{dt}$ — Induced EMF in secondary winding; $P_{in} \approx P_{out}$ — Power balance principle in an ideal transformer

Key Points: Transformers operate on the principle of Mutual Induction.; Energy transfer is contactless, occurring entirely through the magnetic coupling of the core.; The core material (typically laminated silicon steel) is chosen to minimize hysteresis and eddy current losses, facilitating efficient flux flow.

Advantages: Electrical isolation between primary and secondary circuits.; Efficient voltage level transformation with minimal energy loss.

Disadvantages: Requires magnetic material, making the device heavy.; Cannot operate with DC input as the flux would not be time-varying.

Applications: Power transmission and distribution systems.; Impedance matching in electronic circuits.

Additional Info: Option A (cooling coils) is for heat dissipation, not energy transfer.. Option B (air) is an insulator; no electrical transfer occurs through air in standard power transformers.

Answer: C is correct — Energy transfer in a transformer is mediated by the time-varying magnetic flux produced in the core, which links both primary and secondary windings.

Exam Tip: Always remember that transformers are AC devices; the phrase 'time-varying' flux is crucial because constant DC flux would not induce an EMF in the secondary winding.

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