Terminal Voltage and Source EMF Relationship

The relationship between terminal voltage and source EMF (Electromotive Force) can be understood by considering the behavior of a voltage source.

What is a Voltage Source?
A voltage source is a device or circuit element that generates a constant potential difference or voltage across its terminals. It is commonly represented by a battery symbol.

Terminal Voltage
The terminal voltage of a voltage source is the voltage measured across its terminals when it is connected to a load or a circuit. It represents the actual voltage available to the connected circuit.

Source EMF
The source EMF, also known as the electromotive force, is the maximum potential difference or voltage that the voltage source can provide when no current is flowing through it. It represents the internal energy or chemical potential difference of the voltage source.

The Relationship
The relationship between terminal voltage and source EMF can be summarized as follows:

Terminal voltage is always lower than the source EMF.

This means that the actual voltage available to the circuit connected to the voltage source is always less than the maximum potential difference the source can provide.

Explanation:
When a voltage source is connected to a load or a circuit, there is a flow of current through the source due to the internal resistance of the source. This internal resistance causes a voltage drop within the source itself, resulting in a decrease in the terminal voltage.

The terminal voltage can be calculated using the equation:
Terminal Voltage = Source EMF - Internal Voltage Drop

The internal voltage drop is directly proportional to the current flowing through the source and the internal resistance of the source. As the current increases, the internal voltage drop also increases, leading to a decrease in the terminal voltage.

Therefore, the terminal voltage is always lower than the source EMF because of the internal resistance of the source.

Conclusion
In conclusion, the terminal voltage of a voltage source is always lower than the source EMF. This is due to the internal resistance of the source, which causes a voltage drop within the source itself. Understanding this relationship is crucial in designing and analyzing electrical circuits.