Are these formulas applied in electronics applications ?

[axl123]

Right now I'm an 11 grader. Physic is a compulsory subject at school. Right now we have to learn voltage and voltage differences in an electric field. And it's very complicated to understand what it really is. Most of my friends just memorize formulas to pass test but me, I have to understand what it is, the facts about it so that I can remember those formulas.

These are :
VM = WM∞/ q

UMN = AMN/ q

In the book it says (Vietnamese translated to English):
Voltage at a point M represents the ability of electric force to produce potential energy when put an electrically charged particle in M.

Voltage Difference 'tween M and N represents the ability of electric force to produce energy when moving an electrically charged particle from M to N

Just those text aren't enough for me to understand. It has to be something imagery for me to understand what those formulas represents. Like a force, a vector should be good.

It's complicated so I'm thinking if those aren't applied in electronics apps (circuits etc.) then I'm gonna skip them regardless my exams marks (or I'll cheat ). Are they ?

 

[Jony130]

In electric circuit we are interest in a flow of a current. Just like a water flow in pipe the current flow in the wire.
The force that cause the current to flow is a voltage or pressure in water analogy.

Voltage is "electrical pressure", current is a flow of a charge. So voltage is needed to move the charge (current to flow).
Voltage is present at a point or between two points, but voltage do not flow or move as current does.
For example if we have at one end of a wire 300 electron is missing and on the other end of a wire 500 electrons are missing.
Then we have the voltage between the two points.
Both these "points" are positive, but the first point (300 electrons missing) is negative with respect to the second point (500 missing electrons).
And if we connect these points with a conductive wire then current is star to flow. From more negative point to more positive point. And current will flow until the number of electrons on both ends will be equal (no voltage).

And in electronics circuit we don't use these V=W/q formula.
But Votages has something to do with work.
When two similarly charged particles are brought near, they try to repel each other while dissimilar charges attract each other.
This mean every charged particles has ability to do the work (to move charges) . So this ability of a charged particle to do the work is called electric potential.

Try read this article
https://www.electro-tech-online.com/content/222-amp-hour-fallacy-ohm-s-law-noobies.html
Electrical curriculum: watts, ohms, volts, and amps

 

[Ratchit]

axl123,

Yes, those formulas are not very descriptive, are they? Voltage in MKS units is joules/coulomb. That means that voltage is the energy density of the charge. Let's elaborate. It takes energy to bring like charges such as electrons together in close proximity. The energy required to do so divided by the number of electrons is the voltage. If one brings the same set of electrons closer together, it requires more energy to do so, and energy density increases, and by definition the voltage increases. When a voltage is applied across a resistor, the some of the energy of the charges is dissipated as heat when the charges travel through the resistor. So there is less energy left after the charges travel through the resistor. This means the energy density is less and thereby so is the voltage. That is why a resistor "drops" the voltage or the energy density of the charge.

When a capacitor is energized, charges pile up on one side of the plate, and are taken away from the other plate. It takes energy to do that, so a voltage occurs across the capacitor, because it took a number of joules of energy to inbalance the capacitor by a number of coulombs.

Do you get the idea now? Voltage is a density, not a force, does not have a direction, and is not a spacial vector like current is. Charge is going to flow from the higher energy density (voltage) to the lower energy density. Your formulas say charge*voltage=energy(work) which is correct, but not very descriptive.

Ratch

 

[axl123]

Thank you guys all. I now understand. The "electrical pressure" and "energy density" were exactly imagery definitions I was looking for.

 

[kooth]

You have the right idea!

I'm encouraged to hear about a student who wants to learn and not just pass tests! Your curiosity will pay off in more ways than you can ever imagine!

Way to go, and good luck!

Sincerely,

Kooth