Constantan wire resistance 2.5 Ohm, cross-sectional area 2mm2. How long is the wire?

To calculate the length of the taken constantan wire, we will use the formula: R = ρ * l / S, from where we express: l = R * S / ρ.

Constants and variables: R – resistance of the taken constantan wire (R = 2.5 Ohm); S – cross-sectional area (S = 2 mm2); ρ – specific electrical resistance of constantan (at a temperature of 20 ºС ρ = 0.5 Ohm * mm2 / m).

Let’s perform the calculation: l = R * S / ρ = 2.5 * 2 / 0.5 = 10 m.

Answer: The taken constantan wire must have a length of 10 m.