NEIEP Mechanics Practice Exam

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Question: 1 / 475

Given the values Ep=208VAC, Es=35VAC, Ip=3.8amps, Is=21.4amps, what is the efficiency of the transformer?

80%

90%

95%

To determine the efficiency of a transformer, you can use the formula for efficiency, which is defined as the ratio of output power to input power, typically expressed as a percentage. The input power (P_in) is calculated from the primary side, and the output power (P_out) is derived from the secondary side.

1. Calculate the input power:

- Input voltage (Ep) = 208 VAC

- Input current (Ip) = 3.8 amps

- Therefore, P_in = Ep * Ip = 208 V * 3.8 A = 790.4 W

2. Calculate the output power:

- Output voltage (Es) = 35 VAC

- Output current (Is) = 21.4 amps

- Therefore, P_out = Es * Is = 35 V * 21.4 A = 749 W

3. Now, plug these values into the efficiency formula:

- Efficiency = (P_out / P_in) * 100%

- Efficiency = (749 W / 790.4 W) * 100% ≈ 94.7%

When rounded, this value is quite close to 95%. This indicates that the