Carl Fredrik Ahl Posted January 15, 2019 Share Posted January 15, 2019 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? Link to comment Share on other sites More sharing options...
Sensei Posted January 15, 2019 Share Posted January 15, 2019 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). Link to comment Share on other sites More sharing options...
studiot Posted January 15, 2019 Share Posted January 15, 2019 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. Link to comment Share on other sites More sharing options...
mathematic Posted January 15, 2019 Share Posted January 15, 2019 This is not quantum theory - should be in classical physics. Link to comment Share on other sites More sharing options...
Carl Fredrik Ahl Posted January 16, 2019 Author Share Posted January 16, 2019 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? Link to comment Share on other sites More sharing options...
Mordred Posted January 16, 2019 Share Posted January 16, 2019 (edited) 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 Link to comment Share on other sites More sharing options...
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