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Been trying to get my head around Volts, Amps, Ohms and Joules recently.

I am probably missing something very basic that I am finding hard to find an answer for.

I get the basic idea of the following (water comparison):

  • Coulomb = a set amount of electrons (litre)
  • Volts = Pressure at which electrons want to move between 2 points. E.g. the number of electrons in a given space pushing away from each other (Bar)
  • Amps = Amount of electrons that travel through a coulomb in a second. (litres/min)
  • Joule = Unit of Energy e.g. Cost of moving 1 volt through 1 Coulomb (Newton)
  • Ohms = Resistance of electrons moving between 2 points (pipe diameter)

My confusion is with Joules/Amps/Electrons when you add a device to a circuit. (e.g. light bulb)

How correct/incorrect is the above understanding?

Is it not the electrons that get converted into heat, which in turn gets converted into light or would losing electrons cause it to change its physical properties?

After several hours of thinking and researching (while writing this question) is the following missing piece correct?

Joules is the energy, which is the force applied by a cell (power station/battery) onto a circuit (by adding electrons?), e.g. something like Kinetic Energy but for electrons and the light bulb takes some of that energy and by converting it into heat.

Is it correct to think of the following: The light bulb is similar to a water turbine, in a pressured water circuit. The volume of water going in has to be equal to the volume of water going out (if no leaks) which is the amount of electrons. The water turbine spins, and what is lost is the kinetic energy of the water moving (being created by whatever is creating the pressure in the circuit, e.g. pump) and transferred into the turbine.

The reason I ask this is because I have been trying to figure how RCD's work in domestic household circuits. (The physics behind it) And why the Amps are the same going in and coming out.

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TBH, I would, no offence intended, forget the water analogies and try to learn how electromagnetism works, starting with electrostatics , which is the study of electric charges and then moving on to how electricity is generated in power stations and delivered and distributed within your home. Trying to compare it to water is tempting, but harder work than learning from first principles, imo.

Is it not the electrons that get converted into heat, which in turn gets converted into light or would losing electrons cause it to change its physical properties?

No, electrons don't get converted into anything, they can emit photons which energise molecules in your body, causing them to vibrate faster, and you feel this as heat. It's a good bit more complicated than the mental picture you have, unfortunately :)

Best of luck with a more detailed answer.

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Joules is the energy, which is the force applied by a cell (power station/battery) onto a circuit (by adding electrons?)

The joule is the unit we use to measure energy.

Energy is not the same as force, although energy is transferred when a force is applied to a moving object.

In electrostatics, charge carriers don't contain energy within themselves. Rather, a configuration of different charge carriers near each other requires energy to set up. For example, you must supply energy to the system in order to push two electrons near each other, and you must take energy from the system (or increase some other form of energy like the kinetic energy of the electron itself) when you move an electron away from a proton.

In the water analogy, the potential energy of a charge carrier is like the gravitation potential energy of the water. The water behind a dam doesn't have energy just because of what it is, but because of where it is relative to the center of the earth. By allowing the water to flow out of the reservoir, we reduce its g.p.e., and we can use the energy to, for example, turn a turbine and generate electric power.

Note: In the above, I've ignored magnetic field energy. This is a second form of energy that is found in electrical circuits, when there are moving charges. I don't know of any way to relate magnetic energy to the water analogy --- if you want to fully understand electric circuits at some point you have to give up on the water analogy and understand electrostatics as its own field.

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