Use the fact that the resistance of a wire carrying an electrical current is directly proportional to its length and inversely proportional to its cross-sectional area.
If #28 copper wire (which has a diameter of 0.0126 inch)has a resistance of 68.17 ohms per thousand feet,what length of #28 copper wire will produce a resistance of 30.5 ohms?

A)About 447 ft
B)About 442 ft
C)About 432 ft
D)About 452 ft
E)About 462 ft

Question

Use the fact that the resistance of a wire carrying an electrical current is directly proportional to its length and inversely proportional to its cross-sectional area. ​
If #28 copper wire (which has a diameter of 0.0126 inch)has a resistance of 68.17 ohms per thousand feet,what length of #28 copper wire will produce a resistance of 30.5 ohms?
​
A)About 447 ft
B)About 442 ft
C)About 432 ft
D)About 452 ft
E)About 462 ft

Quizplus · Accepted Answer

Given that resistance is directly proportional to length, we can use the formula $R_1/L_1 = R_2/L_2$ where $R_1 = 68.17 \, \Omega$ for $L_1 = 1000$ ft, and $R_2 = 30.5 \, \Omega$. Solving for $L_2$, we get $L_2 = (R_2 \times L_1) / R_1 = (30.5 \times 1000) / 68.17 \approx 447$ ft.

Use the Fact That the Resistance of a Wire Carrying