Voltage and current source in superposition theorem

[wilsonb]

why we take current source as a open and voltage source as a short in superposition theorem. is this is because of its internal resistance or any other reason exist?

 

[rbj]

An ideal voltage source is something that will deliver that specified voltage no matter how much current is required. If you set that voltage spec to 0 (which you do to remove that voltage from the linear equation that depends on it) it is the same as a short circuit. A wire.

An ideal current source is something that will deliver that specified current no matter how much voltage is required. If you set that current spec to 0 (which you do to remove that current from the linear equation that depends on it) it is the same as an open circuit. An insulator.