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.
Thermal EMF's have. polarity and so, for example, one end of a resistor might be a +20uV/Âº generator and the other end. a -20uV/Âº generator. In the ideal situation of both ends of the resistor being at the same temperature, the. thermal EMFs are self-cancelling, resulting in an actual in-circuit thermal EMF near zero. Circuits sensitive. to thermal EMF require consideration to optimize layout to achieve uniform temperatures at each end of. resistor body.