Humans were essentially hunters and gatherers. They had developed the use of fire. B â¦ ut they did not live a settled existence, instead following herds of animals on their migrations which were their primary source of food. Men were the hunters and responsible for the group's primary food source.
Emf - is the amount of energy of any form that is changed into electrical energy per coulomb of charge. pd - is the amount of electrical energy that is changed into other forms of energy per coulomb of charge. Sources of emf: Cell, battery (a combination of cells), solar cell, generator, dynamo, thermocouple.
I dislike the term EMF (Electromotive force) as it is very confusing. Electromotive force, also called emf (denoted $\mathcal{E}$ and measured in volts), is the voltage developed by any source of electrical energy such as a battery or dynamo. Which means that all EMF are voltages but not all voltages are EMF. A voltage is only an EMF if it is a source of energy.