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.
Electromotive force, also called emf (denoted E {\displaystyle {\mathcal {E}}} and measured in volts), is the voltage developed by any source of electrical energy such as a battery or dynamo. It is generally defined as the electrical potential for a source in a circuit. A device that supplies electrical energy is called a seat of electromotive force or emf. Emfs convert chemical, mechanical, and other forms of energy into electrical energy. The product of such a device is also known as emf.