- #1
commelion
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Hi I have been working on this problem and would like to know if I am close to being correct, I am also having difficulty understanding the difference between knowing when to use (vector and magnitude of a vector) relationships correctly, I give an example of this below.
A inductor and resistor (unknown values) are connected in parallel and supplied with a voltage of 120 volts 60 hz. Find the inductance in milli henries if the circuits amp meter reads 5 amps and its watt meter reads 500 watts
Suggested solution
The watt meter measures real power only, therefore I used the following
R = V^2/P and got 28.8 ohms
Magnitude Z = Magnitude V/ Magnitude I
And got Magnitude Z = 24 ohms
Here why is it important to use the magnitude here and not just Z = V/I from (ohms law) ?
I am having difficulty knowing when the correct notation is needed.
I then tried the following for parallel circuits |Z|^-1 = |R^-1+ jWL^-1|
With some algebra I got the following
(1/jWL)^2 = 11 / 20736
jWL = 43.41 ohms
L = 115 milli henries using 2pi*fL
I think this is close to being right if somebody could check this i would be grateful, for the question about the vectors and magnitude notation I have searched on line for an explanation to no avail, hopefully some one here can help.
thanks in advance.
A inductor and resistor (unknown values) are connected in parallel and supplied with a voltage of 120 volts 60 hz. Find the inductance in milli henries if the circuits amp meter reads 5 amps and its watt meter reads 500 watts
Suggested solution
The watt meter measures real power only, therefore I used the following
R = V^2/P and got 28.8 ohms
Magnitude Z = Magnitude V/ Magnitude I
And got Magnitude Z = 24 ohms
Here why is it important to use the magnitude here and not just Z = V/I from (ohms law) ?
I am having difficulty knowing when the correct notation is needed.
I then tried the following for parallel circuits |Z|^-1 = |R^-1+ jWL^-1|
With some algebra I got the following
(1/jWL)^2 = 11 / 20736
jWL = 43.41 ohms
L = 115 milli henries using 2pi*fL
I think this is close to being right if somebody could check this i would be grateful, for the question about the vectors and magnitude notation I have searched on line for an explanation to no avail, hopefully some one here can help.
thanks in advance.