Hello.
Ic=C*dv/dt comes from Q=CV.
V(Voltage across inductor)=L*di/dt comes from what?

I found that integral of (v*dt)=L*integral of (di)
Replacing v by R*I, and replacing I by dq/dt we have that
Integral of (R*dq/dt*dt)=L*integral of (di)
Integral of (R*dq)=L*integral of (di)
OBS.: limits are from 0 and 0 to q and i, respectively.
R*Q=L*I
L=RQ/I

So that means inductance is proportional to the resistance of the inductor?
I think I did a big mistake and a maybe a big confusion but, at least, I tried to find.
The question remains the same.

 

Replacing v by R*I, and replacing I by dq/dt we have that
Integral of (R*dq/dt*dt)=L*integral of (di)

This doesn't work.

The ideal inductor has zero resistance so your second equation above, is nonsense. Where did you get the idea that v = ir in an inductive circuit?

 

Hello.
Ic=C*dv/dt comes from Q=CV.
V(Voltage across inductor)=L*di/dt comes from what?

I found that integral of (v*dt)=L*integral of (di)
Replacing v by R*I, and replacing I by dq/dt we have that
Integral of (R*dq/dt*dt)=L*integral of (di)
Integral of (R*dq)=L*integral of (di)
OBS.: limits are from 0 and 0 to q and i, respectively.
R*Q=L*I
L=RQ/I

So that means inductance is proportional to the resistance of the inductor?
I think I did a big mistake and a maybe a big confusion but, at least, I tried to find.
The question remains the same.

Hi,

If i understand you right i think you want to go back to Faraday which would lead to:
N*dPhi/dt=L*di/dt

for N the number of turns, Phi the magnetic flux, L the inductance, i the current.

or another interesting way to look at it is:
dPhi/di=L/N

 

This doesn't work.

The ideal inductor has zero resistance so your second equation above, is nonsense. Where did you get the idea that v = ir in an inductive circuit?

Haha
That's why I thought I was doing a big mistake
Answering your question, sincerely, I don't know, haha.

Thank you MrAl.

 

Hi,

If i understand you right i think you want to go back to Faraday which would lead to:
N*dPhi/dt=L*di/dt

for N the number of turns, Phi the magnetic flux, L the inductance, i the current.

or another interesting way to look at it is:
dPhi/di=L/N

So it means that N*dPhi/dt=Vl=L*di/dt?
Did Faraday found this?

 

Hi,

Faraday found:
E=N*dPhi/dt
or the signed form:
E=-N*dPhi/dt (i think attributed to Lenz)

L is the constant of proportionality that relates the flux to the current:
L=Phi/I

just as capacitance C is the constant of proportionality that relates the charge to the voltage:
C=Q/V

L has a physical origin just as C has a physical origin, both dependent on the geometry.

Another view is through the stored energy:
U=(1/2)*C*V^2
U=(1/2)*L*I^2

Inductance is the dual of capacitance, so often when you see voltage in a capacitor equation you'll see current in an inductor equation...as current is the dual of voltage.

L is the first letter of Lenz, in his honor (almost same equation as Faraday).

C is the first letter of Capacitor, in honor of Mr. Capacitor (just kidding)

 

Hi,

Faraday found:
E=N*dPhi/dt
or the signed form:
E=-N*dPhi/dt (i think attributed to Lenz)

So it's correct to say that E=-N*dPhi/dt (as my professor said, when I wrote on the board the equation N*dPhi/dt=L*di/dt, "isn't a minus missing?!" Lol) and not E=N*dPhi/dt (incorrect)
Am I right?

 

Hi,

Yes, and i think it was Lenz who clarified the sign of the result, not Faraday, but dont quote me on this rather look it up on the web and maybe you can make a note here in this thread.

 

Hi,

Yes, and i think it was Lenz who clarified the sign of the result, not Faraday, but dont quote me on this rather look it up on the web and maybe you can make a note here in this thread.

I think this is clear in the following page:
http://hyperphysics.phy-astr.gsu.edu/hbase/electric/farlaw.html
Where is attributed to Lenz the minus sign.

 

Hi,

Yes i see they put the little minus sign with the note "Lenz's Law" pointing to it so it modifies Faraday.