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  4. A step-down transformer is used on a 1000V line to deliver 20A at 120V at the secondary coil. If the efficiency of the transformer is 80 % , the current drawn from the line is

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Q. A step-down transformer is used on a $1000V$ line to deliver $20A$ at $120V$ at the secondary coil. If the efficiency of the transformer is $80\%$ , the current drawn from the line is

NTA AbhyasNTA Abhyas 2020

Solution:

$\eta\%=\frac{80}{100}=\frac{V_{s} I_{s}}{V_{p} I_{p}}=\frac{120 \times 20}{1000 \times I_{p}}$
$I_{p}=\frac{120 \times 20}{1000 \times 0.8}=3 \, A$