Which of the following loss varies with the load

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copper loss Explanation: Copper losses, also known as I²R losses, are the electrical energy losses that occur due to the resistance of the transformer windings. Unlike core losses, which remain relatively constant regardless of the load, copper losses are directly proportional to the square of the load current. Working Principle: In a transformer, the primary and secondary currents increase as the load increases. Since power loss in a conductor is given by $P = I^2 R$, the dissipation increases quadratically as more current flows through the windings to meet the demand, making it a variable loss. Key Formulas: $P_{cu} = I^2 R$ — Calculation of copper loss based on winding current and resistance; $P_{total} = P_{core} + I^2 R$ — Total losses in a transformer including fixed and variable components Key Points: Copper losses are variable losses as they depend on the magnitude of the secondary current.; Core losses (Hysteresis and Eddy Current) are considered constant losses because they depend on supply voltage and frequency, which are usually steady.; Maximum efficiency in a transformer occurs when variable copper losses equal constant core losses.; Copper losses are minimized by using windings with low resistance (high cross-section area). Advantages: Useful for calculating efficiency at different load points; Helps in determining the optimal operating point for maximum efficiency Disadvantages: Contributes to heating of windings; Requires high-quality conductor materials to minimize Applications: Transformer efficiency analysis; Design of thermal management systems for electrical machinery Additional Info: Hysteresis and Eddy current losses are collectively called Core or Iron losses, which are fixed at rated voltage.. Option A and B are components of Core loss, which is independent of the load. Answer: C is correct — Copper loss is a variable loss because it depends directly on the square of the load current flowing through the transformer windings. Exam Tip: Always remember that efficiency is maximum when variable losses ($I^2R$) equal constant losses (Core Loss). This is a favorite topic in competitive exams for finding the load at which a transformer is most efficient.

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