In terms of Heat equation it is d2T/dx2 + qgen = qstored assuming steady state, heat flows in one direction. But I have seen examples where energy is balanced in terms of qconv + qcond + qgen= qstored Why is the first equation just not the first derivative of Temperature with respected to x? Why does one equation have second derivative while the other has just one (for example: qcond = -k(dT/dx). For instance, when u calculate heat generated wouldn't the answer be different? I am confused.