Terminal voltage is the potential difference across the terminals of a battery or power supply when a circuit is connected. It is the actual voltage available to external devices, accounting for internal resistance and load resistance.
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Terminal voltage decreases as current increases due to internal resistance within the power source.
It can be calculated using the formula $V_{terminal} = E - Ir$, where $E$ is the electromotive force (emf), $I$ is the current, and $r$ is the internal resistance.
When no current flows (open circuit), terminal voltage equals the emf of the battery.
In practical circuits, terminal voltage is always less than or equal to the emf because of energy loss inside the battery.
Understanding terminal voltage helps in designing efficient circuits by ensuring that components receive adequate voltage.
Review Questions
What happens to terminal voltage as current increases in a circuit?
How do you calculate terminal voltage if given emf, current, and internal resistance?
Why is terminal voltage usually less than the electromotive force in practical circuits?
Related terms
Electromotive Force (emf): The total energy supplied per coulomb of charge by a power source when no current flows.