What is the fluid theory of electricity?

Answer 1

I'll take a stab at it.

Electricity, current flow, is like a liquid in a way. Just like a quantity of liquid enclosed in a container has the potential of making a mess on the floor, a quantity of positive and negative charges develops a potential across a material.

The bigger the mess on the floor, the larger was the volume of liquid to begin with. The release onto the floor of the quantity of liquid caused a current, a stream of liquid, to spill to the floor. The size of that stream is proportional to the amount of liquid available and the rate at which the liquid is spilled. The control of the rate can be viewed as a resistance to the flow of the current of liquid.

Moving to the electric, the larger the potential across the material, the more potential there is for current flow. The current flow is determined by the amount of resistance across the potential. If the resistance is decreased, analogous to the container being tipped more, the amount of current increases. If the resistance is increased the opposite happens.

Hence, it is somewhat intuitive to consider the flow of electricity (the movement of charges) like the flow of a fluid.

In fact, just like a fluid moves easier in a larger pipe, current flows easier in a larger conductor. ...but only to a certain extent is that true. For the reality is electron flow in a conductor is actually due to electron drift from end to end and, depending on the forces involved, sometimes that drift will show bunching of the electrons along the surface of the normally very conductive material, bunching leaving an open area behind towards the center of the material. Hence, what used to be a relatively large material that allowed much electron flow can become a relatively small material and impede electron flow, given the same difference of potential from end to end, solely due to these other factors not being considered in this simple explanation.