Alternating Current: Practice Problem & Solution
45. A 220 volt input is supplied to a transformer. The output circuit draws a current of 2.0 ampere at 440 volts. If the efficiency of the transformer is 80%, the current drawn by the primary windings of the transformer is: (2010 Pre)
Solution Explained:
To solve this problem, we apply the core principles of Alternating Current. Understanding the underlying formula is key to arriving at the correct answer below:
Efficiency of a transformer is given by $\eta = \frac{V_s I_s}{V_p I_p}$.
Substituting the given values: $0.80 = \frac{440 \times 2.0}{220 \times I_p}$.
Rearranging for primary current gives $I_p = \frac{880}{220 \times 0.8} = \frac{4}{0.8} = 5.0 A$.
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