How long is a 0.1mm2 nickel wire required to make a 180 ohm rheostat?

We need to find how long a 0.1 mm ^ 2 nickel wire is required to make a 180 Ohm rheostat.

Let’s start by writing it down:

S = 0.1mm ^ 2;

R = 180 ohms;

we also need for calculations:

pnik = 0.4 * 10 ^ -6 (Ohm * m ^ 2) / m.

We need to find the length of the wire:

l -?

Solution:

Let’s remember the formula for calculating resistance:

R = pnik * l / S.

We express the length from the formula:

S * R = pnik * l;

l = S * R / pnik.

It remains to substitute the values into the formula and perform calculations:

l = (180 * 0.1 * 10 ^ -6) / (0.4 * 10 ^ -6) = 45 meters.