A 25-W soldering iron runs on 110 V dc.What is its resistance?
A)0.0020 Ω
B)4.4 Ω
C)0.48 kΩ
D)2.8 kΩ

Question

Quizplus · Accepted Answer

We can use the formula P = V^2/R, where P is the power (25 W), V is the voltage (110 V), and R is the resistance.

Rearranging the formula to solve for R, we get:

R = V^2/P = (110 V)^2 / 25 W = 4840/25 Ω = 193.6 Ω

However, this is the resistance at room temperature. As the soldering iron heats up, its resistance will increase due to the increase in temperature. So, the actual resistance of the soldering iron when in use may be slightly higher than 193.6 Ω.

Among the given choices, the closest answer to 193.6 Ω is C, 0.48 kΩ.

A 25-W Soldering Iron Runs on 110 V Dc