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

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Homework Help Overview

The discussion revolves around determining the voltage between two points in an electrical circuit, specifically involving a resistor and reactance components. The problem includes calculations related to AC voltage, impedance, and the application of formulas involving resistance and reactance.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the calculation of total impedance (Ztotal) and question the method of combining resistance and reactance. There is an exploration of the correct approach to summing these components in quadrature.

Discussion Status

Participants are actively engaging with the calculations and questioning each other's reasoning. Some guidance has been offered regarding the correct mathematical operations, but there is no explicit consensus on the final answer or method.

Contextual Notes

There is mention of potential confusion in calculations and the emotional state of participants, indicating the pressure of studying and the complexity of the problem. The original poster expresses frustration over arriving at an incorrect answer despite following the steps outlined.

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

PHYSICSHELP_zpse6fd0131.png


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

:o
 
Last edited:
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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)?
 
gneill said:
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)?

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

But I still get the wrong answer :(

I think I may have a mental breakdown...
 
riseofphoenix said:
Oh oops, that's supposed to be a plus...

But I still get the wrong answer :(

I think I may have a mental breakdown...

What value did you calculate?
 
gneill said:
What value did you calculate?

The answer is 96.2 :D
Thanks for catching that!
I think I've been studying for too long
 

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