Which of the following represents the steady state behaviour of heat flow in two dimensions x – y?
1
\(\frac{{{\partial ^2}u}}{{\partial {x^2}}} + \frac{{{\partial ^2}u}}{{\partial {y^2}}} = 0\)
2
\(\frac{{{\partial ^2}u}}{{\partial {x^2}}} + \frac{{{\partial ^2}u}}{{\partial {y^2}}} = {c^2}\)
3
\(\frac{{\partial u}}{{\partial x}} + \frac{{\partial u}}{{\partial y}} = c\)
4
\(\frac{{\partial u}}{{\partial x}} + \frac{{\partial u}}{{\partial y}} = 0\)