3rd Year Electrical Trades Qualification (TQ) Practice Exam

Copper losses in a transformer are caused by winding resistance.

Core losses Magnetic saturation Winding resistance Core cooling

Correct Answer:

Winding resistance

Explanation:

Copper losses come from the resistance of the windings. When current flows through the winding copper, its finite resistance dissipates power as heat, described by P = I^2 R. This loss is localized in the windings and is what we call copper loss. Core losses, in contrast, arise from the magnetic core material—hysteresis and eddy currents—and occur in the core, not the windings. Magnetic saturation is about the core’s flux limit, not a direct loss mechanism, and cooling affects how heat is removed rather than creating the loss itself. So the winding resistance is the source of copper losses.

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