Using a simple mathematical model (with the final quadratic equation), the paper clearly illustrates elevated risks of thermal failure in the electric systems with a negative temperature coefficient of resistance (in particular, for the electronics elements made of carbon and semiconductors). If the temperature coefficient of resistance is positive, the thermal equilibrium exists at any temperature below the melting point. But if the temperature coefficient of resistance is negative, there are three potential cases depending on cooling: (1) for a relatively low cooling rate, a thermal equilibrium is not feasible and the temperature goes up unlimitedly; (2) for a relatively high cooling rate, there are two thermal equilibrium states, stable and unstable; (3) in the borderline case, there is just one unstable thermal equilibrium. As known, the heat produced in an undercooled electric circuit elevates a risk of thermal failure (for instance, Central Processing Units can generate a notable heat and crash if overheated). Such a risk is higher in the electric circuits with negative temperature coefficients of resistance [1-4], in particular for the elements made of semiconductors (silicon, germanium, etc.). The goal is to illustrate the relevant thermal effects using a simple engineering theory.