1. The problem statement, all variables and given/known data A heating coil is to be made, from nichrome wire, which will operate on a 12 V supply and will have a power of 36 W when immersed in water at 373 K. The wire available has a cross-sectional area of 0.10 mm². What length of wire will be required? (Resistivity of nichrome at 273 K = 1.08 x 10-6 Ωm. Temperature co-efficient of resistivity of nichrome = 8.0 x 10-5 K-1.) I think that "Resistivity of nichrome at 273 K = 1.08 x 10-6 Ωm." is meant to say 373K, I will ask tomorrow. 2. Relevant equations ρ=ρ0 [1+α(T-T0 ) ] 3. The attempt at a solution Im thinking that ρ(resistivity) can be changed with P/I^2 then I^2 with V^2/R^2 so i would end up with P*R^2/v^2=ρ0 [1+α(T-T0 ) ] or something like that, I really need some pointers on where to go.