P 3.5-2 Determine the power supplied by each source in the circuit shown in Figure P 3.5-2.

Figure P 3.5-2

To determine the power supplied by each power source we need to find the current through and the voltage across each power source. Again we need to reduce the circuit. Notice the short-circuit wire that shorts out the 7 Ω resistor. Also this wire puts the two current sources in parallel so we can replace the two with one that is 3.5 A pointed upward. The two voltage sources are in series so we can replace them with one 5 V source with the positive terminal on the right. Finally we can add the 20 Ω and the 5 Ω resistors and replace them with a 4 Ω resistor.

So the redrawn circuit looks like

So we can see the current through both voltage supplies is 3.5 A. We need to find the voltage across the two current supplies and we do that by doing a voltage walk. Start at lower left and walk clockwise.

So now we can calculate the power supplied or absorbed by the power supplies. Using the appropriate sign conventions depending on polarity of voltage and direction of current.

Dr. Donovan's Classes Page	Dr. Donovan's PH 320 Homework Page	PH 320 Homework Chapter 3 Page
Dr. Donovan's Main Web Page	NMU Physics Department Web Page	NMU Main Page

Please send any comments or questions about this page to ddonovan@nmu.edu

This page last updated on January 19, 2019