Experiment # 3
Node-Voltage and Mesh-Current Methods
Objective
The objective of this experiment is to relate circuit analysis techniques to actual circuits.
This will be accomplished in our usual fashion, by first analyzing the circuits numerically
“by hand”, then via a computer simulation (PSpice). This theoretical analysis is done in
the preliminary lab exercise. Then, in lab, these same circuits will then be experimentally
examined. The theoretical and experimental values will then be compared in your write
up.
Preliminary Lab Exercise
Node-Voltage Method
The circuit shown in Figure 1 will be used to investigate the node-voltage method of
analyzing circuits (Again, labeled currents flow to the right (for currents in horizontal
branches) or downward (for vertical branches).
I1
R1
A I3
2k
VS1
R3
B
I5
2k
I2
10 k
I4
R2
R5
VS2
R4
20 V
20 k
5k
10 V
0
Figure 1
1. Compute the node voltages VA and VB.
2. Compute the branch currents I1, I2, I3, I4, and I5 using the values of the voltage
sources and the node-voltages computed in the previous step.
3. Use PSPICE to construct the above circuit and run the dc analysis. Compare the result
with the result obtained in step 2.
4. Determine whether the voltage sources are delivering or absorbing power.
Mesh-Current Method
The circuit shown in Figure 2 will be used to investigate the mesh-current method of
analyzing circuits.
1. Compute the mesh-currents IA, IB, and IC (they flow clockwise around the indicated
loops).
2. Compute the branch currents I1, I2, I3, I4, and I5 using the values of the meshcurrents computed in the previous step.
I1
R1
I3
2k
IA
I5
2k
I2
VS1
20 V
R3
R5
10 k
I4
R2
IB
VS2
R4
20 k
5k
IC
10 V
0
Figure 2
3. Use PSPICE to construct the above circuit and run the dc analysis. Compare the result
with the result obtained in step 2.
4. Determine whether the voltage sources are delivering or absorbing power.
Procedure
The circuits of Figures 1 and 2 will now be used to verify the node-voltage and meshcurrent methods, respectively.
Node-Voltage Method
1. Construct the circuit shown in Figure 1.
2. Measure the node-voltages VA and VB using digital multi-meter in the voltmeter
mode.
3. Measure the branch currents I1, I2, I3, I4, and I5 using a properly connected digital
multi-meter in ammeter mode.
2
Mesh-Current Method
1. Construct the circuit shown in figure 2.
2. Measure the branch currents I1, I2, I3, I4, and I5 using a properly connected digital
multi-meter in the ammeter mode.
Analysis
Node-Voltage Method
1. Compare the measured values of the node-voltages VA and VB with the theoretical
values.
2. Compare the measured values of the branch currents I1, I2, I3, I4, and I5 with the
theoretical values.
Mesh-Current Method
1. Compute the value of the mesh-currents IA, IB, and IC from the measured branch
currents and compare with the theoretical values.
2. Compare the measured values of the branch currents I1, I2, I3, I4, and I5 with the
theoretical values.
3