A low-pass filter consists of a 114μF capacitor in series with a 155Ω resistor. The circuit is driven by an AC

Part A

What is the crossover frequency fc?

fc =

Part B

What is Vc when f=1/2 fc?

Part C

What is Vc when f=fc?

### 1 Answer

A) fc = 1/(2*pi*R*C) = 9 Hertz

C) when f= fc, Vc = 0.707(V in)

This is because Xc = R

Vc = (V in)(jXc/(R + jXc) = (V in)(j/(1+j)

|Vc| = |V in|(1/(sqrt 2) = 0.707 Vin

B) when f = 1/2(fc), Vc = 0.89(V in)

Xc = 2R

Vc = (V in)(j2/(1 +j2)

|Vc| = |V in|(2/(sqrt 5) = 0.89(V in)