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Superposition theorem problem

have this question and i just want to make sure i am on the right track as i know there are quite a few steps to this to get to the final soultions


i need to find Current at r1

voltage at r1

current at r2

voltage at r2


i have so far split this into 2 drawings so i am dealing with one power source at a time,

taking r1 and r2 as parallel i found 1/RT to be 2 ohms

so current being 30/2 = 15amps

voltage at r1 current x resistance = 15 x 3 = 45v

i understant now to get the complete answer i would need to do the same with the other power source and combine the figures

Is this correct or have i missed a step out ?
(edited 1 year ago)
Original post by john.ashby
have this question and i just want to make sure i am on the right track as i know there are quite a few steps to this to get to the final soultions


i need to find Current at r1

voltage at r1

current at r2

voltage at r2


i have so far split this into 2 drawings so i am dealing with one power source at a time,

taking r1 and r2 as parallel i found 1/RT to be 2 ohms

so current being 30/2 = 15amps

voltage at r1 current x resistance = 15 x 3 = 45v

i understant now to get the complete answer i would need to do the same with the other power source and combine the figures

Is this correct or have i missed a step out ?


Hi, I am also on this question I am a little confused. If the circuit is in parallel wouldn't you take all 3 resistors instead of R1 and R2 to find Rt?

Also i thought that the E1 and E2 was the voltage?

Could someone explain this to me please

Thanks :smile:
Original post by john.ashby
have this question and i just want to make sure i am on the right track as i know there are quite a few steps to this to get to the final soultions


i need to find Current at r1

voltage at r1

current at r2

voltage at r2


i have so far split this into 2 drawings so i am dealing with one power source at a time,

taking r1 and r2 as parallel i found 1/RT to be 2 ohms

so current being 30/2 = 15amps

voltage at r1 current x resistance = 15 x 3 = 45v

i understant now to get the complete answer i would need to do the same with the other power source and combine the figures

Is this correct or have i missed a step out ?


Original post by olivia0306
Hi, I am also on this question I am a little confused. If the circuit is in parallel wouldn't you take all 3 resistors instead of R1 and R2 to find Rt?

Also i thought that the E1 and E2 was the voltage?

Could someone explain this to me please

Thanks :smile:


I would recommend both of you to watch the following video to "understand" how the superposition theorem works.
https://youtu.be/PRRt15glu_w

The circuit in the video is "similar" to the following circuit given in post #1.



Spoiler



Try this circuit lab to test your answer.
https://phet.colorado.edu/sims/html/circuit-construction-kit-dc-virtual-lab/latest/circuit-construction-kit-dc-virtual-lab_en.html
Reply 3
great this is all useful, i also found this video that explained it very well,
https://www.youtube.com/watch?v=Gk83p3GB-LU&lc=UgzMrhWbL8GvvQW1iO94AaABAg.9pXlEUREpBv9pbKqxEVeRt

so far i have this for 45v source

r1//r2 = 2ohms
r3 = 3 oms
Current Total is 45v/5 = 9amps

then i need to find each current through each resistor
(edited 1 year ago)
Original post by john.ashby
great this is all useful, i also found this video that explained it very well,
https://www.youtube.com/watch?v=Gk83p3GB-LU&lc=UgzMrhWbL8GvvQW1iO94AaABAg.9pXlEUREpBv9pbKqxEVeRt

so far i have this for 45v source

r1//r1 = 2ohms
r3 = 3 oms
Current Total is 45v/5 = 9amps

then i need to find each current through each resistor


You may want to go through the spoiler hint(s) again.

When we "remove" the E2, it is similar to the circuit set-up (left) in your video link at the timestamp (1:40).
Reply 5
Original post by Eimmanuel
You may want to go through the spoiler hint(s) again.

When we "remove" the E2, it is similar to the circuit set-up (left) in your video link at the timestamp (1:40).


the thing that is slightly confusing is, if you focus on voltage E2 at the centre, doesnt current flow in two directions?
so which resistors would be in parallel?
Original post by john.ashby
the thing that is slightly confusing is, if you focus on voltage E2 at the centre, doesnt current flow in two directions?
so which resistors would be in parallel?

I had written them in spoiler. Just click on the plus sign and you see the answer to your question,
I would recommend you think about it why.

If you cannot recognise which resistors are in parallel or series, you would definitely have a problem in doing your exam.
Reply 7
Original post by Eimmanuel
I had written them in spoiler. Just click on the plus sign and you see the answer to your question,
I would recommend you think about it why.

If you cannot recognise which resistors are in parallel or series, you would definitely have a problem in doing your exam.


thank you, i did not even see that hint part on the post, i should have seen the resistors connected in parallel due to the nodes in the circuit
Reply 8
one other thing, is the question not looking for total current and total Voltage, so when you break down the circuit and consider just one power supply do you not need to combine the 2 results ?Screenshot 2023-05-24 at 13.54.46.png
(edited 1 year ago)
Original post by john.ashby
one other thing, is the question not looking for total current and total Voltage, so when you break down the circuit and consider just one power supply do you not need to combine the 2 results ?

You only post the circuit diagram without the question. So I can only speculate what the question wants.
Such questions usually ask for current in the respective resistors which means we need to combine the results.
appolgies,
total current through r1
Voltage across r2
Current through r2
Power dissipated in r3
Voltage at r1

for these i came to
7a
6v
1a
192w
21v
Original post by Eimmanuel
You only post the circuit diagram without the question. So I can only speculate what the question wants.
Such questions usually ask for current in the respective resistors which means we need to combine the results.
Original post by john.ashby
appolgies,
total current through r1
Voltage across r2
Current through r2
Power dissipated in r3
Voltage at r1

for these i came to
7a
6v
1a
192w
21v


If you have checked the answer with Phet, you can be sure that you have obtained the correct answer.
Original post by Eimmanuel
If you have checked the answer with Phet, you can be sure that you have obtained the correct answer.


who is Phet ?
Original post by john.ashby
who is Phet ?

Didn't you use Phet in post #9?

See the bottom right corner.
Original post by Eimmanuel
Didn't you use Phet in post #9?

See the bottom right corner.


hahahhahahahahaha its been a long day at study with the sun blasting through my windows.
No i tried to use formulas etc, i used that when i realised a reply had used it but hidden it
(edited 1 year ago)

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