# What should be the diameter of the iron conductor in order to close an element

**What should be the diameter of the iron conductor in order to close an element with an emf with it? 1.5 V and an internal resistance of 0.2 Ohm, get a current of 0.6 A? The conductor length is 5 m.**

Given:

U = 1.5 Volts – electromotive force of the element;

r = 0.2 Ohm is the internal resistance of the element;

I = 0.6 Ampere – required current strength;

l = 5 meters – conductor length;

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

It is required to determine d (millimeter) – what should be the diameter of the conductor.

Let’s find the resistance that the conductor should have:

U / (R + r) = I;

U / I = R + r;

R = U / I – r = 1.5 / 0.6 – 0.2 = 2.5 – 0.2 = 2.3 Ohm.

Then the cross-sectional area of the conductor will be equal to:

s = k * l / R = 0.098 * 5 / 2.3 = 0.49 / 2.3 = 0.21 mm2.

Then the diameter of the conductor will be equal to:

d = s / n = 0.21 / 3.14 = 0.07 millimeters (n = 3.14 is a geometric constant).

Answer: the diameter of the conductor should be equal to 0.07 millimeters.