An electric current passes through a steel wire. The length of the wire is 180 m, the voltage on it is 120 V, the current is 2 A.

An electric current passes through a steel wire. The length of the wire is 180 m, the voltage on it is 120 V, the current is 2 A. Determine the cross-sectional area of the steel wire. The specific resistance of the steel p = 12 * 10 ^ -8 Ohm * m

L = 180 meters – the length of the steel wire;

U = 120 Volts – voltage of the electrical network;

I = 2 Amperes – the strength of the current flowing through the steel wire;

r = 12 * 10-8 Ohm * m – resistivity of steel.

It is required to determine n (square millimeter) – the cross-sectional area of ​​the steel wire.

Let’s find the total resistance of the steel wire (according to Ohm’s law):

R = U / I = 120/2 = 60 ohms.

Then, to determine the cross-sectional area, you must use the following formula:

R = r * L / n, from here we find:

n = r * L / R = 12 * 10-8 * 180/60 = 12 * 3 * 10-8 = 36 * 10-8 m2 = 0.36 mm2.

Answer: the cross-section of the conductor is 0.36 mm2.