 #1
gfd43tg
Gold Member
 953
 49
Hello,
I had read in my textbook that when a dependent source is in a circuit, and you wish to find the thévenin resistance, then the method to solve for the thevenin resistance is to turn off the independent sources and add an external voltage, then find the external current.
The external voltage divided by the external current will give the thévenin resistance.
However, when the textbook actually does the problem, the example does not even follow the method described. It just adds a short circuit across the terminal and treats it no differently than a problem would have been if there was only independent sources.
I am now confused because they don't follow the method they said works, and I am trying to do it using the method described and cannot get the answer. Also, I know how to convert from thevenin to norton, so just assume I was looking for the thévenin first, and will convert to norton later.
In fact, I will quote the paragraph that is hypocritical
''The equivalentresistance method described previously [independent sources] does not apply to circuits containing dependent sources. Hence, and alternative variation is called for. Independent sources again are deactivated (but dependent sources are left alone) and an external voltage Vex is introduced to excite the citcuit. After analyzing the circuit to determine the current Iex, Rth is found by applying
Rth = Vex/Iex''
This paragraph is a blatant lie as far as I can tell, since the example posted is done using a previous method.
I had read in my textbook that when a dependent source is in a circuit, and you wish to find the thévenin resistance, then the method to solve for the thevenin resistance is to turn off the independent sources and add an external voltage, then find the external current.
The external voltage divided by the external current will give the thévenin resistance.
However, when the textbook actually does the problem, the example does not even follow the method described. It just adds a short circuit across the terminal and treats it no differently than a problem would have been if there was only independent sources.
I am now confused because they don't follow the method they said works, and I am trying to do it using the method described and cannot get the answer. Also, I know how to convert from thevenin to norton, so just assume I was looking for the thévenin first, and will convert to norton later.
In fact, I will quote the paragraph that is hypocritical
''The equivalentresistance method described previously [independent sources] does not apply to circuits containing dependent sources. Hence, and alternative variation is called for. Independent sources again are deactivated (but dependent sources are left alone) and an external voltage Vex is introduced to excite the citcuit. After analyzing the circuit to determine the current Iex, Rth is found by applying
Rth = Vex/Iex''
This paragraph is a blatant lie as far as I can tell, since the example posted is done using a previous method.
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