Power Calculations

1. The problem statement, all variables and given/known data
Concider the circuit shown below. Find the current iR flowing through the resitor. Find the power for each element in the circuit. Which elements are absorbing power?

2. Relevant equations
Ohm’s law: U = IR;
Kirchhoff’s Current Law and Kirchhof’s Voltage Law.

3. The attempt at a solution
My instructor told me that the resistor is supplying power and the voltage is absorbing power. But I just didn’t get it.
By the diagram, the current iR flows in a clockwise direction. With KCL, iR = 2A, and with Ohm’s law, vR = iRR = 10V. But How can I know whether the resistor is absorbing power or supplying power? Because I can’t determine the polarity between the resitor with KVL.
It’s clear that the voltage source is absorbing power, and if it were a battery, it would be charging.
But I can’t understand how can a resistor SUPPLY power to other elements in the circuit as my instructor told me.

Attached Images
File Type: png Screenshot from 2014-03-09 17:43:28.png (7.4 KB)


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