# Download Problem 3.3 Use nodal analysis to determine the current Ix and

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```Problem 3.3 Use nodal analysis to determine the current Ix and amount of power
supplied by the voltage source in the circuit of Fig. P3.3.
I
V
Ix
9A
2Ω
8Ω
+
_ 40 V
4Ω
Figure P3.3: Circuit for Problem 3.3.
Solution: At node V , application of KCL gives
V V V − 40
=0
−9 + + +
2 4
8
1 1 1
40
V
= 9+
+ +
2 4 8
8
7V
= 9+5
8
V = 16 V.
The current Ix is then given by
Ix =
V
16
=
= 4 A.
4
4
To find the power supplied by the 40-V source, we need to first find the current I
flowing into its positive terminal,
I=
V − 40 16 − 40
=
= −3 A.
8
8
Hence,
P = V I = 40 × (−3) = −120 W
(The minus sign confirms that the voltage source is a supplier of power.)
c
All rights reserved. Do not reproduce or distribute. 2013
National Technology and Science Press
```