Potential, Fall of

The change in potential between any two points on an active circuit. The change in potential due to the maintenance of a current through a conductor. The fall in potential multiplied by the current gives work or energy units. The fall of potential in a circuit and its subsequent raising by the action of the generator is illustrated by the diagram of a helix. In it the potential fall in the outer circuit is shown by the descent of the helix. This represents at once the outer circuit and the fall of potential in it. The vertical axis represents the portion of the circuit within the battery or generator in which the potential by the action of the generator is again raised to its original height. In a circuit of even resistance the potential falls evenly throughout it. A mechanical illustration of the relation of fall of potential to current is shown in the cut Fig. 269. A vertical wire is supposed to be fixed at its upper end and a lever arm and cord at its lower end, with weight and pulley imparts a torsional strain to it. The dials and indexes show a uniform twisting corresponding to fall of potential. For each unit of length there is a definite lo of twisting, corresponding to fall of potential in a unit of length of a conductor of uniform resistance. The total twisting represents the total potential difference. The weight sustained by the twisting represents the current maintained by the potential difference. For a shorter wire le twisting would be needed to sustain the weight, as in a shorter piece of the conductor le potential difference would be needed to maintain the same current. IMG:8956969607833025625_430F269.jpg: Fig. 269. MECHANICAL ILLUSTRATION OF