How many meters of nickel-plated wire, with a cut of 0.1 m2, is needed to create a rheostat with a 180 Ohm ax.

To find the required length of nickel wire, we apply the formula: R = ρ * l / S, from where we express: l = R * S / ρ.

Values of variables and constants: R – required resistance of the created rheostat (R = 180 Ohm); S is the cross-sectional area of the wire (S = 0.1 mm2); ρ is the specific electrical resistance of nickelin at 20 ºС (ρ = 0.4 Ohm * mm2 / m).

Calculation: l = R * S / ρ = 180 * 0.1 / 0.4 = 45 m.

Answer: To create a given rheostat, you need to spend 45 m of nickel wire.