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Internal Resistance Formula:
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Internal resistance is the opposition to current flow within a voltage source itself, such as a battery or generator. It causes voltage drop when current is drawn from the source and represents energy losses within the source.
The calculator uses the internal resistance formula:
Where:
Explanation: The formula calculates internal resistance by measuring the voltage drop from open circuit to closed circuit conditions and dividing by the current flowing through the circuit.
Details: Knowing internal resistance is crucial for determining battery health, calculating maximum power transfer, designing efficient power systems, and understanding voltage regulation in electrical sources.
Tips: Enter open circuit voltage in volts, closed circuit voltage in volts, and current in amperes. All values must be positive, and open circuit voltage must be greater than closed circuit voltage.
Q1: What is open circuit voltage?
A: Open circuit voltage is the voltage measured across the terminals of a power source when no load is connected and no current is flowing.
Q2: What is closed circuit voltage?
A: Closed circuit voltage is the voltage measured across the terminals when a load is connected and current is flowing through the circuit.
Q3: Why does internal resistance matter in batteries?
A: Higher internal resistance reduces battery efficiency, causes voltage sag under load, and indicates aging or degradation of the battery.
Q4: How does temperature affect internal resistance?
A: Internal resistance typically decreases with increasing temperature in most batteries and increases with decreasing temperature.
Q5: What are typical internal resistance values?
A: Values vary by battery type - car batteries: 0.01-0.05Ω, AA alkaline: 0.1-0.3Ω, lithium-ion: 0.05-0.2Ω depending on size and condition.