Terminal voltage

Definition

Terminal voltage is the voltage across the terminals of a battery or power source when it is connected to a circuit and delivering current. It reflects the actual voltage available to drive current through the load, taking into account both the electromotive force (emf) of the source and any internal resistance that may reduce the voltage available at the terminals.

5 Must Know Facts For Your Next Test

1. Terminal voltage can be calculated using the formula: $$V_t = ext{emf} - I imes r$$, where I is the current and r is the internal resistance.
2. As current increases through a battery, terminal voltage decreases due to internal resistance, which can affect performance, especially under heavy loads.
3. For an ideal battery with no internal resistance, the terminal voltage equals the electromotive force regardless of the current drawn.
4. When a battery is fully charged, its terminal voltage will be at its maximum; as it discharges, this voltage decreases.
5. Measuring terminal voltage while a circuit is operating provides insight into the battery's health and capacity to supply power.

Review Questions

• How does internal resistance affect terminal voltage in a circuit?
  • Internal resistance has a direct impact on terminal voltage. When current flows through a battery, some voltage is lost due to internal resistance, which can be quantified using the formula: $$V_t = ext{emf} - I imes r$$. This means that as the current increases, more voltage is dropped across the internal resistance, resulting in a lower terminal voltage available to the load.
• In what scenarios would measuring terminal voltage be critical for evaluating battery performance?
  • Measuring terminal voltage becomes crucial in scenarios such as during high-load applications or when troubleshooting devices. If a device isn't performing as expected, checking the terminal voltage under load can indicate whether the battery is capable of supplying sufficient power or if excessive internal resistance is causing significant voltage drops.
• Evaluate how understanding terminal voltage can aid in designing more efficient electrical systems.
  • Understanding terminal voltage allows engineers to optimize designs by accounting for factors like internal resistance and load requirements. By ensuring that components are chosen based on their interaction with the actual terminal voltage under various conditions, designs can minimize energy loss and improve efficiency. Additionally, this knowledge facilitates better battery management systems that monitor performance and extend battery life by preventing over-discharge and maintaining optimal operating conditions.

Related terms

Electromotive Force (emf): The maximum potential difference provided by a battery or power source when no current is flowing.

Internal Resistance: The resistance within a battery or power source that causes a drop in voltage when current flows through it.

Load: Any component or device that consumes electrical energy in a circuit, such as a resistor, light bulb, or motor.