# Homework Help: Omggg Determining voltage between point a and b given R = 40 ohms

1. Mar 8, 2013

### riseofphoenix

Omggg :( Determining voltage between point a and b given R = 40 ohms

This is what I did for part A:

1) ΔVrms = Vmax(1/√2)
ΔVrms = (145)(0.707)
ΔVrms= 102.53

2) Ztotal = √[R² + (XL - XC)²]

XL = 2πfL
XL = 2π(40)(185 x 10^-3)
XL = 46.49

XC = 1/2πfC
XC = 1/[2π(40)(65 x 10^-6)
XC = 1/0.016336382
XC = 61.21

Ztotal = √[40² + (46.49 - 61.2)²]
Ztotal = √(1600 + 216.67)
Ztotal= √(1816.67)
Ztotal = 42.62

3) ΔVrms = (Irms)(Zab)
ΔVrms = (ΔVrms/Ztotal)(Zab)
ΔVrms = (102.53/42.62)(40)
ΔVrms = (2.405)(40)
ΔVrms = 96.2 V

Last edited: Mar 8, 2013
2. Mar 8, 2013

### Staff: Mentor

For your Ztotal, why do you subtract the reactance component from the real (resistance) component when you summed them in quadrature (square root of sum of squares)?

3. Mar 8, 2013

### riseofphoenix

Oh oops, that's supposed to be a plus...

But I still get the wrong answer :(

I think I may have a mental breakdown...

4. Mar 8, 2013

### Staff: Mentor

What value did you calculate?

5. Mar 8, 2013