How does internal resistance affect the terminal voltage of a voltage source when it is delivering current?
Understand the Problem
The question is asking about the effect of internal resistance on the terminal voltage of a voltage source when current is flowing. Internal resistance causes a voltage drop within the source itself, affecting the voltage available at the terminals.
Answer
The terminal voltage decreases as current increases due to the voltage drop across the internal resistance.
When a voltage source delivers current, its terminal voltage decreases due to the voltage drop across its internal resistance. The terminal voltage (V) is equal to the electromotive force (EMF) minus the product of the current (I) and the internal resistance (r): V = EMF - Ir.
Answer for screen readers
When a voltage source delivers current, its terminal voltage decreases due to the voltage drop across its internal resistance. The terminal voltage (V) is equal to the electromotive force (EMF) minus the product of the current (I) and the internal resistance (r): V = EMF - Ir.
More Information
Internal resistance converts some of the electrical energy into heat, reducing the energy available to the external circuit.
Tips
A common mistake is to ignore the effect of internal resistance when calculating the terminal voltage, especially when the current is significant.
Sources
- 21.2 Electromotive Force: Terminal Voltage - UH Pressbooks - pressbooks-dev.oer.hawaii.edu
- 10.1 Electromotive Force – University Physics Volume 2 - pressbooks.online.ucf.edu
- 6.3 Electromotive force and internal resistance - Fiveable - library.fiveable.me
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