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Anonymous Thu 23 Dec 22:14:40 2021 No.14002145 View Reply Original Report

Quoted By: >>14002189 >>14002252 >>14002260 >>14002298

If charge is analogous to mass then why isn't there a mass equivalent to I=dQ/dt. Or the integral of current equals the total charge? What would be the physical meaning of dm/dt? And what would we need to integrate to get mass?

Anonymous

Anonymous Thu 23 Dec 2021 22:26:29 No.14002177 Report

Quoted By:

there is?

Anonymous

Anonymous Thu 23 Dec 2021 22:29:46 No.14002189 Report

Quoted By:

>>14002145
>why isn't there a mass equivalent to I=dQ/dt
It's called mass balance anon, read Transport Phenomena books.

Anonymous

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Anonymous Thu 23 Dec 2021 22:45:53 No.14002252 Report

Quoted By: >>14003030

>>14002145
> then why isn't there a mass equivalent to I=dQ/dt
there is
>What would be the physical meaning of dm/dt?
(mass) flow rate, or mass flux; it's called many things.
> And what would we need to integrate to get mass?
You integrate flowrate over time to get a change in mass. for example, you know the flowrate of all the river dumping into a reservoir, and you know the rate leaving the dam. with mass conservation, you can work out the amount of water in the reservoir.

charge =>mass/volume (when incompressible)
currrent => flowrate
voltage => potential energy/head
resistance => head loss
capacitance => water storage in reservoirs
inductance => mechanical inertia

I fucking love the hydraulic analogy bros

Anonymous

Anonymous Thu 23 Dec 2021 22:47:42 No.14002260 Report

Quoted By:

>>14002145
>Or the integral of current equals the total charge
integral of current DOES equal the change in charge. this is babby's first RC circuit.

Anonymous

Anonymous Thu 23 Dec 2021 22:56:36 No.14002298 Report

Quoted By:

>>14002145
dm/dt is mass flow rate, used a lot even in undergrad thermo

Anonymous

Anonymous Fri 24 Dec 2021 02:20:39 No.14003030 Report

Quoted By: >>14003340

>>14002252
Thanks anon. I mean I realize that if you integrate a rate of change of X you will get X. But sometimes that rate of change has a special name, power, velocity, etc. So I thought perhaps dm/dt had this kind of a special meaning worth assigning a name and a letter. Flowrate seemed to me like a generic description of a rate of something. But if I am wrong then cool.

>inductance => mechanical inertia
but isn't mechanical inertia due to mass? and mass corresponds to Q. and the measure of inductive inertia is L. something doesn't add up. perhaps it is a different kind of inertia, it is typically described as a flywheel. Flywheel is hard to spin up and hard to slow down. Due to inertia. But isn't inertia due to mass? One can argue that Q is also there somewhere, since inductance/inertia prevents the current from changing instantly. And the rate of change of current could be thought of as a second derivative of Q. I don't know if that is even something that is ever viewed from this angle. Further, a changing magnetic field is causing an EMF in the opposite direction. However there is also Flux ?. And it is the change in flux that results in EMF in the opposite direction. And flux is proportional to the magnetic field B which is proportional to H which is proportional to AC current. And AC current means accelerating electrons. So we are back to d^2Q/dt^2. Does that even make sense? What would be the hydraulic analogy to all of these?

Anonymous

Anonymous Fri 24 Dec 2021 03:46:00 No.14003340 Report

Quoted By:

>>14003030
you have inertia from something translating but not rotating, aka moving in a straight line
you can also have inertia from something rotating but not translating, like a flywheel

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