Understand source transformation

In summary, source transformation involves converting between voltage and current sources to simplify a circuit. The Thevenin resistance can be found by short circuiting the voltage source, but the same cannot be done for a current source. If a circuit has both sources, the appropriate method must be used to find the resistance. Source transformation can only be used to change to a voltage source if the current source and resistors are in parallel. Other tricks can be used to simplify circuits with current sources in series with resistors. In the case of a voltage source in series with a resistor, it can be changed to a current source, but this cannot be done if they are in parallel.
  • #1
Air
203
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I'm trying to understand source transformation and with my research, I have had some confusion. I have two question regarding them and would appreciate any help.


  1. I understand that the thevenin resistance is found by short circuiting the voltage source. Is that also the case when you short circuit the current source? What if it has both sources, what resistance do we find when we short circuit them?
  2. By using source transformation, can we only change to voltage source if the current source and the resistors are in parallel?

Thanks in advance.
 
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  • #2


Air said:
  1. I understand that the thevenin resistance is found by short circuiting the voltage source. Is that also the case when you short circuit the current source? What if it has both sources, what resistance do we find when we short circuit them?
  2. By using source transformation, can we only change to voltage source if the current source and the resistors are in parallel?

1. You simply make a current source an open circuit. If you think of it a current source keeps the current in one branch constant, if you take it out, there would be no current.

2. Yep.
 
  • #3


Kruum said:
1. You simply make a current source an open circuit. If you think of it a current source keeps the current in one branch constant, if you take it out, there would be no current.

2. Yep.

1. So if you take out the current source, it's not the same as taking out voltage source. By taking voltage source out, you can find thevenin resistance. By taking current source out, you find nothing? Is that what you are saying? :confused:

2. Great. So if the current source and the resistor are in series then we cannot use source transformation to change to voltage source?
 
  • #4


Air said:
1. So if you take out the current source, it's not the same as taking out voltage source. By taking voltage source out, you can find thevenin resistance. By taking current source out, you find nothing? Is that what you are saying? :confused:

No, you can take the current source out. You just can't short circuit it otherwise your resistance will be wrong.

2. Great. So if the current source and the resistor are in series then we cannot use source transformation to change to voltage source?

Unfortunately, no. But there are usually some other tricks we can use to make the circuit easier.
 
  • #5


Kruum said:
No, you can take the current source out. You just can't short circuit it otherwise your resistance will be wrong.

So, if I'm to find the thevenin resistance and have been given both voltage source and current source, is the best method to convert the current source to the voltage source then short circuit the current source?

Kruum said:
Unfortunately, no. But there are usually some other tricks we can use to make the circuit easier.

Hmmm... Can you briefly explain what to do if current source and the resistor are in series and we wish to change to voltage source?
 
  • #6


Air said:
So, if I'm to find the thevenin resistance and have been given both voltage source and current source, is the best method to convert the current source to the voltage source then short circuit the current source?

You could do that. But then again you can take the current source out and replace it with an open connection.

Hmmm... Can you briefly explain what to do if current source and the resistor are in series and we wish to change to voltage source?

If you have a current source in series with a resistor, there is nothing you can do to change the current source into voltage source. I meant that you can make the circuit easier by using some other tricks. Sorry for confusing you, I'm not natively English.
 
  • #7


Kruum said:
You could do that. But then again you can take the current source out and replace it with an open connection.

Great, Thanks.

Kruum said:
If you have a current source in series with a resistor, there is nothing you can do to change the current source into voltage source.

Cool. I have a final question regarding this. If the voltage source and the resistor is in series, then it can be changed to current source? If the voltage source and the resistor is in parallel then it cannot be changed to current source?

Kruum said:
Sorry for confusing you, I'm not natively English.

It's ok. You have helped me a lot and your language has been very clear.
 
  • #8


Air said:
If the voltage source and the resistor is in series, then it can be changed to current source? If the voltage source and the resistor is in parallel then it cannot be changed to current source?

That's right.
 
  • #9


If you have a current source in series with a resistor, you can eliminate the resistor from your circuit.
The same is true for a resistor in parallel with a voltage source.
 
  • #10


CEL said:
If you have a current source in series with a resistor, you can eliminate the resistor from your circuit.
The same is true for a resistor in parallel with a voltage source.

Providing you have the appropriate circuit to do so.
 

1. What is source transformation?

Source transformation is a technique used in circuit analysis to simplify complex circuits by replacing voltage sources with equivalent current sources or vice versa. This allows for easier calculation of circuit parameters and analysis of circuit behavior.

2. How does source transformation work?

Source transformation works by using Kirchhoff's voltage and current laws to replace a voltage source with a series resistor and current source or to replace a current source with a parallel resistor and voltage source. This process maintains the same circuit behavior while simplifying the circuit structure.

3. When should source transformation be used?

Source transformation is particularly useful when analyzing circuits with multiple voltage or current sources, as it can help reduce the number of equations that need to be solved. It is also helpful when trying to find the Thevenin or Norton equivalent of a circuit.

4. What are the benefits of using source transformation?

Source transformation can simplify complex circuits, making them easier to analyze and understand. It can also reduce the number of equations needed to solve a circuit, making calculations more efficient. Additionally, it can help identify equivalent circuits, such as Thevenin or Norton equivalents, which can be useful in certain circuit analysis techniques.

5. Are there any limitations to source transformation?

Source transformation is not always applicable and may not work for all types of circuits. It is important to carefully consider the circuit structure and behavior before deciding to use source transformation. Additionally, source transformation may introduce some error into calculations, so it should be used with caution and cross-checked with other analysis techniques.

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