What is the internal resistance of a Current Source and what should it be replaced with: Short circuit or Open Circuit?
2 Answers
The internal resistance of a **current source** should ideally be **infinite**. This means that in an ideal current source, the internal resistance is very high, allowing it to maintain a constant current regardless of the load connected to it.
When analyzing circuits with current sources:
- If you need to **remove or replace** an ideal current source during circuit analysis (e.g., in Thevenin or Norton equivalent circuits), you replace the current source with an **open circuit**.
Thus, the internal resistance is high (ideally infinite), and the current source is replaced with an open circuit when deactivated.
When analyzing circuits with current sources:
- If you need to **remove or replace** an ideal current source during circuit analysis (e.g., in Thevenin or Norton equivalent circuits), you replace the current source with an **open circuit**.
Thus, the internal resistance is high (ideally infinite), and the current source is replaced with an open circuit when deactivated.
The internal resistance of an ideal current source is zero. This is because an ideal current source is designed to supply a constant current regardless of the voltage across it. In practical terms, however, real current sources do have some internal resistance, which can affect their performance.
### Internal Resistance of a Current Source
1. **Ideal Current Source**: The internal resistance is theoretically zero. This means the current source can maintain its specified current even if the voltage across it changes.
2. **Real Current Source**: It will have a non-zero internal resistance. This internal resistance impacts how closely the actual current source can approximate the ideal behavior. The real source's internal resistance is typically small but not zero.
### Replacing a Current Source in Circuit Analysis
When analyzing circuits, you often need to replace a current source with a model that simplifies the analysis. This replacement depends on the context of the analysis:
1. **Short Circuit Replacement**: In the context of Thevenin's theorem or when looking to simplify a network where the current source is ideal, you would replace the current source with a short circuit. This is because an ideal current source can supply any amount of current with zero internal resistance, so for analysis purposes, you assume that it can conduct current with no voltage drop across it.
2. **Open Circuit Replacement**: When considering a practical, real-world current source, you might model it by its internal resistance and other characteristics. However, for simplifying circuit analysis involving a real current source, it is not common to replace it with an open circuit. An open circuit would imply no current flow, which does not accurately represent the behavior of a real current source.
### Summary
- **Ideal Current Source**: Replace with a short circuit for analysis.
- **Real Current Source**: For practical purposes, replace it with its internal resistance or model it according to its characteristics, but not with an open circuit.
In circuit theory, the key is to understand whether you are dealing with an ideal or practical source and choose the replacement accordingly to simplify the analysis.
### Internal Resistance of a Current Source
1. **Ideal Current Source**: The internal resistance is theoretically zero. This means the current source can maintain its specified current even if the voltage across it changes.
2. **Real Current Source**: It will have a non-zero internal resistance. This internal resistance impacts how closely the actual current source can approximate the ideal behavior. The real source's internal resistance is typically small but not zero.
### Replacing a Current Source in Circuit Analysis
When analyzing circuits, you often need to replace a current source with a model that simplifies the analysis. This replacement depends on the context of the analysis:
1. **Short Circuit Replacement**: In the context of Thevenin's theorem or when looking to simplify a network where the current source is ideal, you would replace the current source with a short circuit. This is because an ideal current source can supply any amount of current with zero internal resistance, so for analysis purposes, you assume that it can conduct current with no voltage drop across it.
2. **Open Circuit Replacement**: When considering a practical, real-world current source, you might model it by its internal resistance and other characteristics. However, for simplifying circuit analysis involving a real current source, it is not common to replace it with an open circuit. An open circuit would imply no current flow, which does not accurately represent the behavior of a real current source.
### Summary
- **Ideal Current Source**: Replace with a short circuit for analysis.
- **Real Current Source**: For practical purposes, replace it with its internal resistance or model it according to its characteristics, but not with an open circuit.
In circuit theory, the key is to understand whether you are dealing with an ideal or practical source and choose the replacement accordingly to simplify the analysis.