Nodal analysis, setting up the equations

[gomezfx]

Homework Statement

[PLAIN]http://img844.imageshack.us/img844/8508/circuit.png

Homework Equations

KCL set ups

The Attempt at a Solution

I am having trouble setting up the KCL equations

The 30V voltage source on the left with the resistor is messing me up, how do I incorporate that?

Do I just do 30/15 and assume a 2A current source is going into node A?

Here are my equations:

VD = reference node = 0 V

KCL @ Node B
(VB-VA)/25 + (VB-VC)/50 - 1 + 4 = 0

KCL @ Node C
(VC-VD)/50 + (VC-VB)/50 + 1 = 0

KCL @ Node A?
(VA-VB)/25 + (VA-VD)/31.25 - 4 + ?? = 0

 

[ehild]

You have 30V at the other end of the 15 ohm resistor. So the current through it is (VA-30)/15.

ehild

 

[gomezfx]

You have 30V at the other end of the 15 ohm resistor. So the current through it is (VA-30)/15.

ehild

Ok, then the entire equation for voltage at node A is:

(VA-30)/15 + (VA-VB)/25 + (VA-VD)/31.25 - 4 = 0?

After I solve for all the voltages at the nodes, how do I find power at the independent voltage a current sources?

Do I just use voltage drops?
IE, Power at 4A = (VA-VB)*4

 

[ehild]

Ok, then the entire equation for voltage at node A is:

(VA-30)/15 + (VA-VB)/25 + (VA-VD)/31.25 - 4 = 0?

This is correct.

After I solve for all the voltages at the nodes, how do I find power at the independent voltage a current sources?

Do I just use voltage drops?
IE, Power at 4A = (VA-VB)*4

Yes, knowing the potential difference U across the terminals of a source and the current I flowing through it, the power is U*I.ehild