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GATE 2015 EE – Question 28

Electric Circuits · Network solution methods: KCL, KVL, Node and Mesh analysis · 1 mark · Multiple choice

The voltages developed across the $3\ \Omega$ and $2\ \Omega$ resistors shown in the figure are 6 V and 2 V respectively, with the polarity as marked. What is the power (in Watt) delivered by the 5 V voltage source?

Networks N1 and N2 are connected by three parallel branches: a $3\ \Omega$ resistor with 6 V across it, a $2\ \Omega$ resistor with 2 V across it of the opposite polarity, and a 5 V voltage source.
  1. 5
  2. 7
  3. 10
  4. 14

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Show answer and explanation

Correct answer: (A) 5

Explanation

The $3\ \Omega$ resistor carries $\frac{6}{3} = 2$ A from N1 to N2 and the $2\ \Omega$ resistor carries $\frac{2}{2} = 1$ A in the opposite direction, so the net resistor current from N1 to N2 is 1 A. By KCL the voltage source carries 1 A back, and it delivers $5 \times 1 = 5$ W.