Electrical metaphor

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Home : 2005 : February : 17

Electrical metaphor
By Kevin

I find that for most applications (excluding the quantum details of certain electronic components) that flowing water is quite effective. An EMF or battery is like a pump that moves the water, a resistor is like a waterwheel
that takes energy from the falling water out of the system (i.e. turns it into heat), a capacitor is like a dam, keeping the water level high on one side and low on the other. Inductors are a bit more challenging with this metaphor, since inductance is really rather unique to electromagnetism. I suppose that you could think of inductors as being a loop of water outside your main flow.

When water from your circuit flows through the inductor, it is slowed down by paddle wheels in contact with the other loop (the loop that is part of the inductor). As the water in the other loop speeds up to the same speed as the water in your circuit, the inductor no longer impedes flow. If the current in your circuit changes direction, the water flowing in the inductor loop resists the change and tries to keep your circuit flowing in the same direction.

To summarize:
Simple electrical circuits can be treated as water flows.
Current (I) can be analogized to water current (speed).
Voltage (V) can be analogized to water height (another form of potential). The higher the water, the higher the voltage. Even introduce negative voltage by having water levels lower than some arbitrary zero level.
Resistance (R) can be analogized to a water wheel (Larger resistance means a more heavily loaded wheel) that uses current against its resistance to turn the potential in to energy (almost exactly equivalent to V=IR and P = I^2 R).
Inductance (L) can be related to a second loop of water that must be sped up or slowed down by your circuit and that resists the change in current. (The mathematics probably don't come out correctly, i.e. LRC circuit calculus won't come out right, but that's probably not what you are looking for.)
Capacitance (C) can be related to a dam which prevents water from crossing and allows a buildup of different water heights on either side.

Hope this helps and isn't too long to read.