# Terminal voltage

Equivalent circuit diagram of a real linear voltage source (with consumer)
Characteristic curve of a linear source with internal resistance in interaction with a linear consumer

Terminal voltage ( English terminal voltage ) or terminal voltage is a term used in electrical engineering . It describes the electrical voltage (symbol ) that can be measured between the two connections of a current source or voltage source . ${\ displaystyle U}$

According to the adjacent figure, the terminal voltage is the difference between the open circuit voltage and the product that is formed from the current intensity and the output resistance (also called internal resistance) (in general the impedance :) of the voltage source . Alternatively, the current strength multiplied by the load resistance (general ) results . ${\ displaystyle U _ {\ text {kl}}}$ ${\ displaystyle U_ {0}}$${\ displaystyle I \ cdot R _ {\ text {i}}}$${\ displaystyle I}$${\ displaystyle R _ {\ text {i}}}$${\ displaystyle Z _ {\ text {i}}}$${\ displaystyle U _ {\ text {kl}}}$ ${\ displaystyle R _ {\ text {V}}}$${\ displaystyle Z _ {\ text {V}}}$

${\ displaystyle U _ {\ text {kl}} = U_ {0} -I \ cdot R _ {\ text {i}} \ quad}$ or simply ${\ displaystyle \ quad U _ {\ text {kl}} = I \ cdot R _ {\ text {V}}}$

When a linear voltage source is loaded, i.e. when its current is drawn, the terminal voltage drops depending on the current intensity until it is zero in the event of a short circuit (special case of current adjustment ). The terminal voltage has the highest value when no current is flowing because the terminals are open, i.e. in no-load operation (special case of voltage adjustment ). With power adjustment, the terminal voltage is half as large as the open circuit voltage.

The terminal voltage allows conclusions to be drawn about the nature, correct function and quality of the source, as the formulas (with known linear load resistance) can be used to calculate both the open circuit voltage and the output resistance of the source.

## literature

• F. Möller, H. Frohne, K.-H. Löscherer, H. Müller: Fundamentals of electrical engineering (guidelines for electrical engineering). BG Teubner, Stuttgart, ISBN 3-519-46400-4