4 questions · 8% of the Calculations exam
Why A is correct
For a resistive single-phase load, power equals voltage times current. Multiplying 240 volts by 25 amperes gives 6,000 watts; the square-root-of-three multiplier belongs to balanced three-phase calculations.
Why B is correct
Balanced three-phase apparent power is 1.732 times line voltage times line current. Multiplying 1.732 by 208 volts by 20 amperes gives approximately 7,205 volt-amperes.
Why A is correct
Three-phase real power is 1.732 × voltage × current × power factor. The calculation is 1.732 × 480 × 35 × 0.85 = 24,731 watts, or approximately 24.7 kW.
Why B is correct
For two parallel resistances, reciprocal values add: 1/12 + 1/6 = 3/12 = 1/4. The equivalent resistance is therefore 4 ohms; 18 ohms would be the series result.
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