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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