Few Questions on source tranformation

[clurt]

It's question 1b) Please view attached

1. Just to clarify, when different voltage sources are in series you pick the smaller one?

2. First step, they turned the 1A and 2ohm into 2V, why does the resistance disappear? Then between the last two steps the 12/7 ohm resistance remains with 18/7 voltage. Why does one resistance disappear while the other doesn't?

Thanks on advance

 

[clurt]

http://m.imgur.com/PM25nEB,BlRd503Additional source

 

[NascentOxygen]

It's question 1b) Please view attached

It would have been better if you'd cropped the attachment to just the relevant block in post #1 and in the process made it more legible.

1. Just to clarify, when different voltage sources are in series you pick the smaller one?

No! The 3v comes about because two sources are in series, +6v and -3v, so the resultant voltage is their sum with polarities taken into account.

2. First step, they turned the 1A and 2ohm into 2V, why does the resistance disappear?

It doesn't. The solution is in error. I expect the right side 2 ohm was probably intended to be labelled 4 ohms.

Then between the last two steps the 12/7 ohm resistance remains with 18/7 voltage. Why does one resistance disappear while the other doesn't?

Nothing disappears. The two resistors are in parallel, so they can be replaced by an equivalent one of the value equal to that when two resistors are in parallel.

Hope that helps.

 

[NascentOxygen]

This thread belongs in the homework sub-forum. You almost certainly would have received prompt assistance had you listed it there.

Could a mentor kindly move this to the appropriate forum ...

 

[alphy]

I am always happy to clarify and explain concepts related to source transformation. To answer your first question, when different voltage sources are in series, the voltage across each source is the same. Therefore, it is not a matter of picking the smaller one, but rather recognizing that they are equivalent and can be replaced by a single source with the same voltage.

In the second question, the resistance disappears in the first step because of the use of Ohm's law (V=IR). By converting the 1A current and 2ohm resistance into a voltage, we can see that the voltage source is equivalent to the original current and resistance. This simplifies the circuit and makes it easier to perform the next steps.

In the next step, the 12/7 ohm resistance remains because it is in parallel with the 18/7 voltage source. In parallel circuits, the voltage across each component is the same, but the current is divided between them. This is why the resistance remains, as it is still a part of the circuit and affects the overall current flow.

I hope this helps to clarify the process of source transformation. If you have any further questions, please do not hesitate to ask. As scientists, it is important to fully understand and question concepts in order to deepen our understanding and knowledge.