Operating resistance of a 30-watt light bulb designed for a 28-volt system?

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Enhance your understanding of the fundamentals of electricity with the AMT General Exam. Study with multiple-choice questions crafted to improve your knowledge and confidence. Prepare effectively for your success!

Multiple Choice

Operating resistance of a 30-watt light bulb designed for a 28-volt system?

Explanation:
For a resistive load operated at a specified voltage and power, the resistance is found from R = V^2 / P. Here, a 30-watt bulb at 28 volts gives R = 28^2 / 30 ≈ 26.1 ohms, so the operating resistance is about 26 ohms. This matches how it would behave: the current would be I = V / R ≈ 28 / 26.1 ≈ 1.07 A, and P = V × I ≈ 30 W. If the resistance were much higher, like 28 ohms, you'd get 28 W instead of 30 W; if it were much lower, like around 1 ohm, the power at 28 volts would be hundreds of watts.

For a resistive load operated at a specified voltage and power, the resistance is found from R = V^2 / P. Here, a 30-watt bulb at 28 volts gives R = 28^2 / 30 ≈ 26.1 ohms, so the operating resistance is about 26 ohms. This matches how it would behave: the current would be I = V / R ≈ 28 / 26.1 ≈ 1.07 A, and P = V × I ≈ 30 W. If the resistance were much higher, like 28 ohms, you'd get 28 W instead of 30 W; if it were much lower, like around 1 ohm, the power at 28 volts would be hundreds of watts.

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