Using the relation R = E^2 / P, what is the resistance of a device that draws 48 watts from a 24-volt source?

Using the relation R = E^2 / P, what is the resistance of a device that draws 48 watts from a 24-volt source?

• A. 24 ohms
• B. 48 ohms
• C. 6 ohms
• D. 12 ohms

Answer: (D)

This question tests how resistance relates to voltage and power through the relation P = V^2 / R, which rearranges to R = V^2 / P. With a 24-volt supply and 48 watts drawn, compute R as 24^2 / 48 = 576 / 48 = 12 ohms. You can confirm by finding the current first: I = P / V = 48 / 24 = 2 A, then R = V / I = 24 / 2 = 12 ohms. The resistance is 12 ohms.

This question tests how resistance relates to voltage and power through the relation P = V^2 / R, which rearranges to R = V^2 / P. With a 24-volt supply and 48 watts drawn, compute R as 24^2 / 48 = 576 / 48 = 12 ohms. You can confirm by finding the current first: I = P / V = 48 / 24 = 2 A, then R = V / I = 24 / 2 = 12 ohms. The resistance is 12 ohms.