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Kirchoff's Rules Physics Help?
Using Kirchhoff's rules (and given emf1 = 70.8 V, emf2 = 61.6 V, emf3 = 79.8 V) calculate the following:
Picture of system here- http://www.webassign.net/sercp/p18-23alt.gif
(a) Find the current in each resistor shown in the figure above.
IR1 =
IR2 =
IR3 =
(b) Find the potential difference between points c and f.
emf =
1 Answer
- DHLv 71 decade agoFavorite Answer
We have three unknowns I1 (to the left), I2 (up); and I3 (left)
This is my notation..If the value of I turns out to be negative then the direction is opposite to that assumed
We need 1 node eqn and two loop eqns
I1 + I2 + I3 = 0
Left loop
E1 - E2 + I2*R2 - I1*R1 = 0
So -2000R1 + 3000R2 = E2-E1 = -9.2
Rt loop
-3000R2 + E2 + 4000R3 - E3 = 0
So -3000R2 + 4000R3 = E3 - E2 = 79.8-61.6 = 18.2
We set up matrices to solve this
1 1 1 I1 = 0
-2000 3000 0 I2 = -9.2
0 -3000 4000 I3 = 18.2
The solution is I1 = 3.77x10^-4A
I2 = -2.82x10^-3A
I3 = 2.44x10^-3A
Vcf = -I2*R2 + E2 = -(-2.82x10^-3)*3000 + 61.6 = 70.1V
