- #1
biglake
- 3
- 0
Im having a bit of trouble with some problems using Kirchoff's rules.
The problem states for me to calculate each of the unknown currents: I1, I2, & I3 for the circuit diagram attached.
Now I've drawn my diagram and I've gotten my three equations for three unknowns, but i keep getting a negative number for the final answers for I1 and I2. I3 ends up being way off.
Equations:
1. I3 = I1 + I2
2. 8 = -2.0 I1 – I3
3. 4 = I3 – 2I2
4. 6 = -I1 – I2
The equations come from the following:
1. Conservation of energy rule
2. Top loop
3. Bottom Loop
4. Outside Loop
This is the way that my professor was having us practice them in class.
Using equation #2 and substituting equation #1 into #2 I arrive at the following:
Work:
8 = -2.0I1 – I3
8 = -2.0I1 – (I1 +I2)
8 = -3.0I1 – I2
Then Solving for I2 on equation #4 I got:
I2 = -I1 – 6
Including this into the previous equation I got
8 = -3.0I1 – (-I1 – 6)
8 = -3.0I1 - I1 - 6
8 = -4.0I1 -6
14 = -4.0I1
Dividing
-3.5 = I1
The proper answer is +3.5
Ive worked the problem over and over and I can't seem to see where I got a sign mixed up. If someone could steer me in the right direction I would be very thankful.
The problem states for me to calculate each of the unknown currents: I1, I2, & I3 for the circuit diagram attached.
Now I've drawn my diagram and I've gotten my three equations for three unknowns, but i keep getting a negative number for the final answers for I1 and I2. I3 ends up being way off.
Equations:
1. I3 = I1 + I2
2. 8 = -2.0 I1 – I3
3. 4 = I3 – 2I2
4. 6 = -I1 – I2
The equations come from the following:
1. Conservation of energy rule
2. Top loop
3. Bottom Loop
4. Outside Loop
This is the way that my professor was having us practice them in class.
Using equation #2 and substituting equation #1 into #2 I arrive at the following:
Work:
8 = -2.0I1 – I3
8 = -2.0I1 – (I1 +I2)
8 = -3.0I1 – I2
Then Solving for I2 on equation #4 I got:
I2 = -I1 – 6
Including this into the previous equation I got
8 = -3.0I1 – (-I1 – 6)
8 = -3.0I1 - I1 - 6
8 = -4.0I1 -6
14 = -4.0I1
Dividing
-3.5 = I1
The proper answer is +3.5
Ive worked the problem over and over and I can't seem to see where I got a sign mixed up. If someone could steer me in the right direction I would be very thankful.