I’m walking to present you what negative voltage is by putting John right into a hole. Together you’ll easily learn, it’s nothing weird or mystical.

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Meet John. That is 1.8 meters (6 feet) tall.

What go it typical that john is 1.8 m tall? can you discover his elevation by just looking at his head?

No. You have to compare the top of his head come the ground the is standing on to be able to find his height. That man is 1.8 m tall really way that the optimal of his head is 1.8 m higher than the ground that he stands on.

It’s the same thing through voltage. You can’t say anything around the voltage there is no comparing the to one more point.

It’s usual to define a zero allude (0V), or ground, in a circuit.

In a straightforward battery circuit, the ground allude is usually the minus terminal of the battery. For this reason if someone says that “this allude is 5V”, they usually mean it’s 5V compared to ground.

## Putting man in a Hole

Back to John. What if we dig a feet of 1.8 meters, then placed John into the hole. (Poor John).

His feet are currently 1.8 meters listed below the ground.

Another way of saying this is the his feet room at MINUS 1.8 meters.

John is still the specific same person, he’s just put differently compared to the ground. Thus the place of his feet i do not care negative.

It’s the same with voltage.

For example, imagine 2 9V batteries.

Remember – a battery gift 9V method the add to terminal is 9V higher than the minus terminal.

Now, let’s take one battery and say that its minus terminal is walking to be the soil (0V) in our circuit.

What happens if we connect the to add of the second battery to the minus of the first one (i.e. We affix it come ground)?

Nothing yes, really happens v the batteries. They’re specifically the very same as castle were before connecting them.

And no present flows.

But what is the voltage top top the minus terminal the the 2nd battery?

Since the minus is 9V reduced than the plus, and since the plus is linked to ground, the minus would have to be minus 9V.

So we have developed a negative voltage of 9V.

Or have we?

If friend look closely, we haven’t yes, really created anything.

We’ve simply labeled the plus of the 2nd battery 0V.

And we’ve labeled the minus that the second battery -9V, due to the fact that it’s 9V reduced than 0V.

## When carry out You Need negative Voltage?

It’s not so lot that friend “need” negative voltage. However sometimes girlfriend get negative voltage in a circuit, and it’s an excellent to recognize what that is.

One instance where girlfriend get an adverse voltage is in the astable multivibrator circuit.

Sometimes you see circuits that require a strength supply with three connections, because that example, +9V, 0V, and also -9V. This is an extremely common for amplifier circuits.

But they might too have said that the circuit requirements +18V, +9V, and 0V (GND). It would have actually been the exact same thing, simply with various names.

## Questions?

If you uncover these class useful, girlfriend should examine out Ohmify. It’s an digital academy for electronic devices where you learn every little thing from just how voltage functions to just how you can architecture a microcontroller circuit.

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