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.
Back Electro-motive Force is voltage generated in a motor while in operation. Decoders can monitor this voltage for control purposes. A decoder can use Back Electro-Motive Force (BEMF) as a governor. This feature prevents trains from slowing down or speeding up on grades.