Electronics > Beginners

Some noob questions

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Mr D:
OK, i'll take it on faith that it's not important to focus on and won't dwell on it much longer.

It just seems unintuitive to me that a circuit would work correctly if that actual flow would be the reverse of what we imagine when designing it. For example, a complicated garden sprinkler system with valves wouldn't (presumably) work if the water flow was reversed.

james_s:
A sprinkler is an open loop, water flows through the pipes, comes out the sprinklers and lands on the lawn. Your goal with the sprinklers is to take water from a source and relocate it to the lawn. With electricity you need a circuit, the electrons are flowing in a loop around and around, you can't see them anyway so what difference does it make which direction they're flowing? The reason conventional flow is backwards in the first place is that for the first hundred years or so of working with electricity it was impossible to tell the actual direction of flow. As long as everything is consistent it makes no difference at all. The reason designing a circuit works when the flow is backwards is that all the symbols are drawn backwards too. The direction the actual electrons are moving is completely irrelevant because you can't see them anyway.

Mr D:
OK, for the moment i'll ignore it.

So that brings me to ground.

Until now i've only been thinking about closed circuits involving batteries and resistors.

But how does ground tally with this?

Attached are images of two circuits. According to EveryCircuit they both produce the same current. But how can this be?

In one, the positive and neg. terminals are not connected (because the flow leaves the resistor and enters another enormous resistor called the Earth?!)

Until now i have been presuming that to have a circuit with flow, the pos. and neg. terminals must be connected.

Mr. Scram:

--- Quote from: Mr D on August 17, 2018, 07:18:49 am ---OK, for the moment i'll ignore it.

So that brings me to ground.

Until now i've only been thinking about closed circuits involving batteries and resistors.

But how does ground tally with this?

Attached are images of two circuits. According to EveryCircuit they both produce the same current. But how can this be?

In one, the positive and neg. terminals are not connected (because the flow leaves the resistor and enters another enormous resistor called the Earth?!)

Until now i have been presuming that to have a circuit with flow, the pos. and neg. terminals must be connected.

--- End quote ---
You're close to the answer, but take the wrong turn just before the end. What makes you think Earth is a giant resistor? You might want to look at what's needed to make a properly earthed connection before you answer that. An extra hint is that telegraph wires often are singular wires, not pairs.

Mr D:
So if you take a 9 volt battery, attach a wire to each terminal, then hold one terminal in one hand, and the other terminal in the other hand, then your body, is it not, acting as a resistor? And the amount of current flowing through your body will determined by Ohm's law.

Now, replace your body with the earth under your feet, stick one wire in the ground, and the other wire in the ground a meter away, then the planet
Earth is also acting like a resistor?

Or is this not what is meant by "ground" in a circuit?

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