How Voltage is Measured in Circuits?

[Carl Fredrik Ahl]

Hi,

I know that voltage is the potential energy, but I wonder how it's measured. For example, how do they measure the hall voltage in magnetic sensors (image attached), or how do smartphones measure the voltage in the battery to show the battery life?



[Sensei]

Quote

How Voltage is Measured in Circuits?

Take a look at the simplest analog voltmeter. It contains resistor with known resistance, very high value like 1 Mega Ohm. Wire goes through electromagnet. There is also solid magnet. When current is flowing through wire, electromagnet is turned on, and repels from solid magnet. The larger current, the more powerful electromagnet, thus needle is repelled more on the scale.

Ohm's law is I=U/R, so U=I*R. R is constant 1 MOhm. So U is proportional to I.

The difference between analog voltmeter and analog ammeter is just in this additional resistor. If you switch to ammeter mode, resistor is bypassed.

 

49 minutes ago, Carl Fredrik Ahl said:

I know that voltage is the potential energy,

No, it's not. E=Q * U, so U=E/Q. Voltage is electric potential energy (in Joules) divided by charge (in Coulombs).

[studiot]

46 minutes ago, Carl Fredrik Ahl said:

I know that voltage is the potential energy

Stop right there and follow Sensei's very sensible advice to checkout the basics first.

You have this wrong.

Voltage is not any kind of energy. (Although it is easy for primary teachers to make that mistake)

It takes around 3 million volts per metre to create a static discharge (spark) in the air.
This may bite a bite if it catches your finger, but it won't really hurt you.
Because the energy involved is minute.

Yet a standard 12 volt vehicle battery has more than enough energy to kill a man.

So start with Ohm's Law, like everybody else.

 

[mathematic]

This is not quantum theory - should be in classical physics.

[Carl Fredrik Ahl]

17 hours ago, Sensei said:

Take a look at the simplest analog voltmeter. It contains resistor with known resistance, very high value like 1 Mega Ohm. Wire goes through electromagnet. There is also solid magnet. When current is flowing through wire, electromagnet is turned on, and repels from solid magnet. The larger current, the more powerful electromagnet, thus needle is repelled more on the scale.

Ohm's law is I=U/R, so U=I*R. R is constant 1 MOhm. So U is proportional to I.

The difference between analog voltmeter and analog ammeter is just in this additional resistor. If you switch to ammeter mode, resistor is bypassed.

 

No, it's not. E=Q * U, so U=E/Q. Voltage is electric potential energy (in Joules) divided by charge (in Coulombs).

Thx for the answer, but I wanted to know how digital voltmeters works.

8 hours ago, mathematic said:

This is not quantum theory - should be in classical physics.

Ok, can I change that?

[Mordred]

8 hours ago, mathematic said:

This is not quantum theory - should be in classical physics.

 

4 minutes ago, Carl Fredrik Ahl said:

 

Ok, can I change that?

!

Moderator Note

No but I can I will consider that a request

 

Edited January 16, 2019 by Mordred