Using Kirchhoff's rules to calculate current

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To calculate the currents in the circuit using Kirchhoff's laws, the user initially finds I1 and I2 as 1A and 2A, respectively. The confusion arises with the calculation of I3, where the user applies Kirchhoff's voltage law but overlooks the need to account for the combined currents at the nodes. It's essential to apply Kirchhoff's current law (KCL) at the junctions where currents converge, particularly noting that I3 contributes to the current through the 8.00 Ohm resistor. By correctly labeling and accounting for the net currents at the nodes, the user can resolve the calculations for I3 accurately. Understanding and applying both KCL and KVL is crucial for solving circuit problems effectively.
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1. Calculate the three currents indicated in the circuit diagram below.

I have attached the diagram.

How would I use Kirchhoff's laws to find the currents I am getting thrown off by the third loop.
 

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trevorwisc said:
1. Calculate the three currents indicated in the circuit diagram below.

I have attached the diagram.

How would I use Kirchhoff's laws to find the currents I am getting thrown off by the third loop.


How are you "getting thrown off by the third loop"? You'll have to show your attempt at a solution so we can see how to help.
 
gneill said:
How are you "getting thrown off by the third loop"? You'll have to show your attempt at a solution so we can see how to help.

Solution attempt:

I1 loop 9.00V-9.00(I1)=0 so I1=1A
I2 loop 12.00v-6.00(I2)=0 so I2=2A
For I3 loop 12.00V-10(I3)-8(I1)-1(I2)=0 by plugging in I1 and I2 I get I3 to be 5A.
 
trevorwisc said:
Solution attempt:

I1 loop 9.00V-9.00(I1)=0 so I1=1A
I2 loop 12.00v-6.00(I2)=0 so I2=2A
For I3 loop 12.00V-10(I3)-8(I1)-1(I2)=0 by plugging in I1 and I2 I get I3 to be 5A.

Ah. Don't forget to apply KCL at the nodes where currents join/split. For the "I1 loop", for example, I3 joins the party at the rightmost node, so the current through the 8.00 Ohm resistor is actually I1 + I3. Label the net currents on wires around the nodes.
 

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