1. The internal resistance of an ideal current source is infinite. 2. Current generators are modelled as an ideal current source in parallel with a resistor. 3. For an ideal current source , this means replace the current source with an open circuit. 4. A resistive circuit is a circuit containing only resistors, ideal current sources , and ideal voltage sources. 5. One notes that now each problem is relatively simple, since it involves only one single ideal current source . 6. For example, consider an inductor in series with an ideal current source & mdash; a physically impossible configuration. 7. In practice the ideal current source is replaced by a current mirror, which is less ideal in two ways. 8. If I were doing this " professionally ", I would do what someone suggested above : Consider operating a ideal current source ". 9. :: For ideal current sources in series, there would have to be two different currents in the same wire, which is impossible. 10. Thus, an ideal current source , if such a thing existed in reality, could supply unlimited power and so would represent an unlimited source of energy.