Superposition Theorem:
The superposition theorem is a principle used to analyze linear electric circuits that contain multiple independent sources. It states that the voltage across (or current through) an element in a linear circuit is the algebraic sum of the voltages across (or currents through) that element due to each independent source acting alone.

Effect of One Current Source:
When applying the superposition theorem to analyze the effect of one current source in a circuit, we consider the effect of that current source only and ignore the other sources (voltage sources). This means that all the other voltage sources in the circuit are shorted.

Explanation:
When we consider the effect of one current source in a circuit using the superposition theorem, we assume that all the other voltage sources are shorted. This is because in a linear circuit, a current source can be represented as a short circuit, meaning it will provide a constant current regardless of the voltage across it.

By shorting the other voltage sources, we eliminate their influence on the circuit and focus solely on the effect of the current source. This simplifies the analysis and allows us to determine the voltage across or current through the desired element caused by the current source alone.

By shorting the voltage sources, we essentially reduce the circuit to a simpler form where only the current source and the elements connected to it are considered. This allows us to calculate the voltage or current using Ohm's law or other applicable circuit analysis techniques.

It is important to note that the superposition theorem assumes the circuit is linear, meaning the relationship between voltage and current in the circuit elements is linear (Ohm's law is valid). Additionally, the theorem only applies to circuits with independent sources, where the sources are not dependent on the circuit variables.

In conclusion, when applying the superposition theorem to analyze the effect of one current source in a circuit, we short all the other voltage sources in the circuit to eliminate their influence and simplify the analysis.