Can someone please help me find expressions for i2, i3 and i5?
I know i1 must be Vin-Vx/R1.
i3 is theoretically Vx-Vout/R2, but im stuck at i5 and i2.
Thank you very much.
Can someone please help me find expressions for i2, i3 and i5?
I know i1 must be Vin-Vx/R1.
i3 is theoretically Vx-Vout/R2, but im stuck at i5 and i2.
Thank you very much.
As others have pointed out, the only difference between a resistor and capacitor in calculating the current is the capacitor has a complex impedance while the resistor has just a real impedance which is called the resistance. This means we have to use complex numbers to calculate the current.
For the resistor we have:
i=v/R
and for the cap we have:
i=v/Z
where Z is the complex impedance:
Z=1/(j*w*C)
and j is the imaginary operator and w is the angular frequency equal to 2*pi*f with f the frequency in Hertz.
This is sometimes shortened to:
Z=1/(s*C)
where s=j*w.
So if we assume you know the voltage across the cap is v then we have:
i=v/z=v/(1/(s*C))
and using algebra:
i=v*s*C/1=v*s*C
and since s=j*w we end up with:
i=v*j*w*C.
This is purely imaginary which means the current is 90 degrees out of phase with the voltage.
You have to be a little careful though because here we use the impedance not the reactance. Impedance is usually represented with a Z while reactance is usually represented with an X. If we try to use reactance instead of impedance we end up with a real quantity and that is not entirely correct.