Internal resistance

Definition

Internal resistance is the resistance within a battery or any other voltage source that causes a loss in the output voltage as current flows through it. It is an intrinsic property of the source, often affecting the overall efficiency of electrical circuits.

5 Must Know Facts For Your Next Test

1. Internal resistance causes a drop in the terminal voltage of a battery when current flows.
2. It is typically denoted by $r$ and measured in ohms ($\Omega$).
3. The internal resistance can be determined using the formula $V = \mathcal{E} - Ir$, where $V$ is the terminal voltage, $\mathcal{E}$ is the electromotive force (emf), and $I$ is the current.
4. As internal resistance increases, the efficiency of power delivery decreases.
5. In practical applications, lower internal resistance in batteries and power supplies is generally preferred.

Review Questions

• How does internal resistance affect the terminal voltage of a battery?
• What formula relates electromotive force (emf), terminal voltage, current, and internal resistance?
• Why is lower internal resistance preferred in practical applications?

Related terms

Electromotive Force (emf): The total energy supplied per coulomb of charge by a source when no current flows. It represents the maximum potential difference across the terminals.

Terminal Voltage: The voltage output of a device measured across its terminals. When current flows, it is less than the emf due to internal resistance.

Ohm's Law: $V = IR$, where $V$ is voltage, $I$ is current, and $R$ is resistance. This law describes how electrical properties interact in a simple resistive circuit.