Concept:For a 100% efficient (ideal) transformer, the power entering the primary coil equals the power exiting the secondary coil.
Formula:$$ V_p I_p = V_s I_s $$
Solution:- Given: Primary voltage \( V_p = 220 \text{ V} \).
- Secondary voltage \( V_s = 1800 \text{ V} \) and Secondary current \( I_s = 22 \text{ A} \).
- Rearrange the power conservation formula to solve for the primary current (\( I_p \)):
$$ I_p = \frac{V_s I_s}{V_p} $$
- Substitute the values:
$$ I_p = \frac{1800 \times 22}{220} $$
- Simplify:
$$ I_p = 1800 \times \left( \frac{22}{220} \right) = 1800 \times 0.1 = 180 \text{ A} $$
Why other options are incorrect:A common mistake is using the wrong ratio (e.g., dividing by 1800 instead of 220), which would result in drastically incorrect current values. Because it's a step-up transformer (voltage increases ~8x), the primary current must be ~8x larger than the secondary current.
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