A hydroelectric power plant situated at a distance of 20 km from a town. Whose energy demand is 100 MW at 240 V. At hydro electric power plant, the water pressure head is at a height of 400 m and the water flow available is \( 100\,\mathrm{m^3/s} \). Electrical energy generated in power plant is transmitted to the town with the use of transformers voltage output of the AC generator at power plant is stepped up and is there transmitted over long distances to a sub-station near the consumers in town. Sub-stations and utility poles steps down the voltage finally the 240 V which finally reaches the houses.
Which amongst the following is not responsible for energy loss in transformer due to heat?
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Flux leakage
The energy losses of a real transformer are of two kinds: losses that are dissipated as heat in the windings or the core, and losses due to imperfect magnetic coupling, which are not heat.
Option (1) Flux leakage — Not a heating loss. Some flux of the primary does not link the secondary, so less energy is transferred; this is a loss of coupling, not heat produced in the transformer.
Option (2) Resistance of the windings — A heating loss. The current in the copper windings produces Joule heat \( I^2R \).
Option (3) Eddy currents — A heating loss. The changing flux induces eddy currents in the iron core, which heat it.
Option (4) Hysteresis — A heating loss. The core is magnetised and demagnetised in every cycle, and the energy of each hysteresis loop appears as heat in the core.
NCERT (2026-27):
Transformers – “… But in actual transformers, small energy losses do occur due to the following reasons:
(i) Flux Leakage: There is always some flux leakage; that is, not all of the flux due to primary passes through the secondary due to poor design of the core or the air gaps in the core. …
(ii) Resistance of the windings: The wire used for the windings has some resistance and so, energy is lost due to heat produced in the wire (I2R). …
(iii) Eddy currents: The alternating magnetic flux induces eddy currents in the iron core and causes heating. …
(iv) Hysteresis: … The resulting expenditure of energy in the core appears as heat and is kept to a minimum by using a magnetic material which has a low hysteresis loss.”