The wires inside a cable each have there own plastic insulation .why does the insulasion have diffrent colours

A cable is a bundle of two wires or three wires or a thousand wires,
inside a single 'tube'.  In order for the cable to be useful, you need to
be able to match each wire at one end of the cable to the same wire
at the other end.  If each wire has a different physical appearance,
then it's easy.

This is what a calorimeter is used for simpler ex, to measure calories in food.

stands for electromotive force and it is measured in volts. despite its name, it is not actually the force in the sense of being a "pushing" or "pulling" (not measured in newtons).an equation that relates emf,  ℰ,  to a battery's terminal voltage, v, current, i, and internal resistance, r, is    ℰ = v + irin this case, the emf can be interpreted as a voltage—a difference in electric potential.i would not say that it would be considered an energy. if emf can be defined as the energy/work per a unit charge from a battery or other electric source, then it is not strictly energy.