For metallurgical reasons, it is desirable to melt the weld metal with minimum energy input. Which one of the following heat sources is most consistent with this objective: (a) high power, (b) high power density, (c) low power, or (d) low power density?

The correct option is;

(a) High power density

Explanation:

The power density of a material is the amount of power per unit volume of the material. Power density, in the context of transformers, fuel cells, batteries, motors, and power supply units, is measured with respect to the volume, and the units is given as W/m³

A system such as a capacitor with an high power density has the capacity to put out large energy amount from a small volume. A capacitor with a high power density, can produce the same power output as a car battery and is said to have a high power density.