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Irms, Vrms and power calculations

by NoConflict
Tags: calculations, irms, power, vrms
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NoConflict
#1
Apr12-12, 04:43 PM
P: 1
1. The problem statement, all variables and given/known data

Basically, I need to understand how to calculate Irms and I*rms given a Vrms and an impedance Z.

Example question:
Given Vrms = 120 V at an angle of 30 and an impedance of Z = 10 Ω, find Irms and I*rms.


2. Relevant equations

How exactly do I solve for Irms and I*rms?


3. The attempt at a solution

I figure that Irms = Vrms / Z. However I am a bit confused as to the I*rms.

From my notes, I would imply that I just flip the sign of the angle, but this does not seem right.

My attempt:

Irms = Vrms/Z = 120angle30/10angle0 = 12angle30
And for I*rms, just flip the sign of the angle: 12angle-30
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gneill
#2
Apr12-12, 04:59 PM
Mentor
P: 11,626
Quote Quote by NoConflict View Post
1. The problem statement, all variables and given/known data

Basically, I need to understand how to calculate Irms and I*rms given a Vrms and an impedance Z.

Example question:
Given Vrms = 120 V at an angle of 30 and an impedance of Z = 10 Ω, find Irms and I*rms.


2. Relevant equations

How exactly do I solve for Irms and I*rms?


3. The attempt at a solution

I figure that Irms = Vrms / Z. However I am a bit confused as to the I*rms.

From my notes, I would imply that I just flip the sign of the angle, but this does not seem right.

My attempt:

Irms = Vrms/Z = 120angle30/10angle0 = 12angle30
And for I*rms, just flip the sign of the angle: 12angle-30
Yup. basically that's it. I* represents the complex conjugate, which for a complex number means that the sign of the imaginary component of the number is inverted. This has the effect of inverting the sign of the angle in polar form.


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