# physics circuit question

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#1
X=3Ω , Y=6Ω, Z=18Ω and the battery has e.m.f 12V, and it says total resistance of circuit is 6Ω - i did 12/6 to work out the current in the battery using I=V/R , but i'm now stuck on the question which is calculate the current in Z and also the current in X. It then says work out the p.d across X I have attached the image of the circuit below.
Last edited by gogman12345; 1 month ago
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1 month ago
#2
(Original post by gogman12345)
X=3Ω , Y=6Ω, Z=18Ω and the battery has e.m.f 12V, and it says total resistance of circuit is 6Ω - i did 12/6 to work out the current in the battery using I=V/R , but i'm now stuck on the question which is calculate the current in Z and also the current in X. It then says work out the p.d across X I have attached the image of the circuit below.
Do you know what the p.d. across Z is? If so, and since you know its resistance, you should be able to work out the current in it.

You've already said that you've worked out the current in the circuit before it splits across the two branches, so if you now also know the current in Z, you should be able to find the current in the other branch.

Finally, knowing the current in X and its resistance, finding the p.d. across it should be easy.
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#3
(Original post by Pangol)
Do you know what the p.d. across Z is? If so, and since you know its resistance, you should be able to work out the current in it.

You've already said that you've worked out the current in the circuit before it splits across the two branches, so if you now also know the current in Z, you should be able to find the current in the other branch.

Finally, knowing the current in X and its resistance, finding the p.d. across it should be easy.
Is there a way to work out what the p.d across Z is with the information i gave?
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1 month ago
#4
(Original post by gogman12345)
Is there a way to work out what the p.d across Z is with the information i gave?
Do you know Kirchhoff's second law? If so, apply it to the loop including the battery and Z.
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#5
(Original post by Pangol)
Do you know Kirchhoff's second law? If so, apply it to the loop including the battery and Z.
sorry to bother you again here is a photo of the questions - for 2bi i got 9 for ci i got 2 but im stuck on the rest of the questions. I sort of understand kirchoffs second law but don't know how to apply it
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1 month ago
#6
(Original post by gogman12345)
sorry to bother you again here is a photo of the questions - for 2bi i got 9 for ci i got 2 but im stuck on the rest of the questions. I sort of understand kirchoffs second law but don't know how to apply it
Kirchhoff's second law says that in a closed loop in a circuit, the sum of the e.m.f.s is equal to the sum of the p.d.s. This is a statement of the conservation of energy - it is saying that the total energy into the loop (per unit charge) is equal to the total energy out of the loop (per unit charge).

Follow the loop that starts from one side of the battery, goes through Z, and back to the battery. There is only one e.m.f., that due to the battery. There is only on p.d., that across Z. So what is the p.d. across Z?
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#7
(Original post by Pangol)
Kirchhoff's second law says that in a closed loop in a circuit, the sum of the e.m.f.s is equal to the sum of the p.d.s. This is a statement of the conservation of energy - it is saying that the total energy into the loop (per unit charge) is equal to the total energy out of the loop (per unit charge).

Follow the loop that starts from one side of the battery, goes through Z, and back to the battery. There is only one e.m.f., that due to the battery. There is only on p.d., that across Z. So what is the p.d. across Z?
the overall e.m.f is 12v so would the p.d be 12 meaning that cii= 12/18= 0.6reccuring and then ciii 12/9 = 1.3reccuring and 1.3r+0.6r = 2
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1 month ago
#8
(Original post by gogman12345)
the overall e.m.f is 12v so would the p.d be 12 meaning that cii= 12/18= 0.6reccuring and then ciii 12/9 = 1.3reccuring and 1.3r+0.6r = 2
Not sure what you mean by the last part, but that looks OK. Don't give recurring answers, you need to give final answers to an appropriate number of significant figures.
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#9
(Original post by Pangol)
Not sure what you mean by the last part, but that looks OK. Don't give recurring answers, you need to give final answers to an appropriate number of significant figures.
ok thanks for all the help in the last part i meant that both currents added up to the current of the battery
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