# Similarity between P&ID and Electrical diagrams?

1. Oct 4, 2015

### Neitrino

Dear Forum Memebrs,

in some instances the flow of fluid in P&ID diagram is similar to the flow of electrical current in circuit boards: in order to have an electric current you have to have a potential difference across two points (which is called voltage across two point s)thus defining potentials at each junction of complicated electrical circuit one can identify the flow of current, so much the same to have a fluid flow across two points you have to have a pressure differential...

Thanks

2. Oct 4, 2015

### Staff: Mentor

It is true that many people use this analogy. Both fluid pipes and wired circuits conserve energy and mass/charge. But to go beyond that, the analogy can be very misleading, so engineers and scientists discourage it.

3. Oct 4, 2015

### meBigGuy

Fluid flow is a useful analogy to initially explain electricity to someone with absolutely no electronics background. Unfortunately, people make a "hobby" out of stretching the analogy too far. It's best to think in terms of ohms law (E=IR) and the inductor (V=Ldi/dt) and capacitor ( I = Cdv/dt) equations and the associated equations for power and energy.

Ohm's law, E=IR, simply says the current through a resistance increases with voltage.

Also, understanding the units is helpful, for example that 1 ampere of current flow is a flow of 1 coulomb/second where a coulomb is a unit of charge equal to 6.241×1018 electrons.

Volts are a bit more complex, representing potential energy per unit of charge or joules/coulomb. In other words, 1 joule of energy change will be imparted to every coulomb of charge passing though two points that have 1 volt of potential difference. You could say that's like a hydraulic pressure drop, but why bother? (to be honest, I seldom think of a volt this way. I just think of it as a volt.)

1 watt is the power dissipated when a coulomb of charge changes by 1 volt every second (or 1 joule per second)

Just reading over those relationships until they feel intuitive (and trying to visualize what is being expressed) is the best way to really get a grasp on electricity.