Internal resistance

Definition

Internal resistance is the opposition to the flow of current within a battery or power source, causing a voltage drop when current flows. It affects the terminal voltage and efficiency of the power source.

5 Must Know Facts For Your Next Test

1. Internal resistance causes a reduction in the terminal voltage compared to the electromotive force (EMF) of a power source.
2. The internal resistance can be modeled as a resistor in series with an ideal voltage source.
3. As current increases, the voltage drop across the internal resistance increases, reducing terminal voltage.
4. Internal resistance is typically measured in ohms ($\Omega$).
5. Factors like temperature, age, and chemical composition of batteries affect their internal resistance.

Review Questions

• How does internal resistance affect the terminal voltage of a battery?
• What happens to terminal voltage as current through a battery increases?
• Name at least two factors that can influence the internal resistance of a battery.

Related terms

Electromotive Force (EMF):

The maximum potential difference between two terminals of a power source when no current is flowing.

Terminal Voltage:

The voltage output of a power source when it is delivering current to a load.

Ohm’s Law: $$V = IR$$, which relates voltage ($$V$$), current ($$I$$), and resistance ($$R$$).