1. ECE 201 Circuit Theory 11 Source Transformation to Solve a Circuit Find the power associated with the 6 V source. State whether the 6 V source is absorbing or delivering power to the circuit.

2. ECE 201 Circuit Theory 12 Which method to solve? Use mesh-current method and solve for the current in the 6 V source. (3 equations) Use node-voltage method and solve for the voltage across the 30Ω resistor and calculate the current delivered by the 6 V source.

3. ECE 201 Circuit Theory 13 Use Source Transformation to “focus in” on the branch containing the 6V source. CAUTION --- Preserve the identity of the branch containing the 6V source!

4. ECE 201 Circuit Theory 14 Step 1-- Transform the 40 V source

5. ECE 201 Circuit Theory 15 Step 2 (a) -- combine the 20Ω and 5Ω resistors into an equivalent 4Ω resistor. R eq = 4Ω Step 2 (b) -- transform the equivalent 4Ω resistor and the 8A current source into a 32 V source in series with a 4Ω resistor.

6. ECE 201 Circuit Theory 16 Step 3 -- Transform the 32 V source in series with 20Ω into a 1.6 A source in parallel with a 20 Ω resistor.

7. ECE 201 Circuit Theory 17 Step 4 (a) -- Combine the 30Ω and 20Ω resistors into an equivalent 12 Ω resistor. Step 4(b) -- Transform the equivalent 12 Ω resistor in parallel with the 1.6 A source into a 19.2 V source in series with a 12 Ω resistor. R eq = 12Ω

8. ECE 201 Circuit Theory 18 The final circuit has preserved the branch containing the 6 V source. The current can be determined by i

9. ECE 201 Circuit Theory 19 i The actual current is flowing from right to left, into the + terminal of the 6 V source. Therefore, the 6 V source is absorbing power.