How many meters of 0.2 mm ^ 2 nickel wire did it take to make a 30 Ohm slide rheostat?

To find the length of the nickelin wire consumed for the manufacture of the considered slider rheostat, we use the formula: R = ρ * l / S, whence we express: l = R * S / ρ.

Values of constants and variables: R – resistance of the slide rheostat (R = 30 Ohm); S is the cross-sectional area of the wire (S = 0.2 mm2); ρ is the specific electrical resistance of nickelin (ρ = 0.4 Ohm * mm2 / m).

Calculation: l = R * S / ρ = 30 * 0.2 / 0.4 = 15 m.

Answer: It took 15 meters of nickel wire.