What is the length of an iron wire if its resistance is 4 ohms and its cross-sectional area is 0.3mm ^ 2?

Given:

R = 4 Ohm – resistance of the iron wire;

s = 0.3 mm2 (square millimeters) is the cross-sectional area of the wire;

r = 0.098 Ohm * mm2 / m – iron resistivity.

It is required to determine l (meter) – the length of the iron wire.

To determine the length of the iron wire, you must use the following formula:

R = r * l / s, from here we find that:

l = R * s / r;

l = 4 * 0.3 / 0.098 = 1.2 / 0.098 = 12.2 meters (the result has been rounded to one decimal place).

Answer: The length of the iron wire is 12.2 meters.