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Open and Closed Case
When we teach electricity to new techs, we use a lot of “water” metaphors. We talk about volts like PSI, amps like flow, and watts like GPM (speaking of GPM in HVAC, check out our article on hydronics HERE). Even the word “flow” gives us a vision of water moving.
When we talk switches and circuits, we say “open” to mean no path/no flow and “closed” to mean a path or flow.
That's the opposite of water.
With water, we “open” the tap when we want flow, and we close it to stop the flow.
With a switch, we “close” when we make a circuit, and we “open” when we break a circuit.
Someone pointed out to me that describing an “open” switch or circuit like a drawbridge may be better. Cars (electrons) can move when the bridge is closed and cannot move when the bridge is open.
It struck me that this water metaphor may be one reason newbies struggle to grasp relays.
Or maybe I'm just overthinking it.