# Simple nodal analysis

Discussion in 'Homework Help' started by Quintilis_Telescope, Oct 17, 2009.

1. ### Quintilis_Telescope Thread Starter New Member

Oct 13, 2009
10
0
Hello. This one is so simple but Im having trouble using nodal analysis. Superposition would be easier but my prof wants me to use nodal.

Find the voltage at A. The answer is 5.7V ~, but I don't know how to get there.

Here are my equations I got that are wrong:

I3 = I1-I2

VA/1kΩ = ((15-VA)/1.197KΩ) - (VA/3.29kΩ)

and

I6 = I4-I5

VA/3.29kΩ = ((5V-VA)/1.197kΩ) - (VA/1kΩ)

Thankyou.

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2. ### The Electrician AAC Fanatic!

Oct 9, 2007
2,661
471
You only have one unknown, so you only need one equation.

The idea of the nodal method is to use Kirchoff's current law. The sum of the currents entering and leaving node A must be zero.

So, write an equation summing the currents in the 4 resistors to zero:

V/3290 + V/1000 + (V - 15)/1197 + (V - 5)/2212 = 0

Solve for V.

3. ### Quintilis_Telescope Thread Starter New Member

Oct 13, 2009
10
0
ah. that makes sense. So far previously ive only done problems with 2 unknowns so this one got me confused. Thanks.