1. What is Internal Resistance?

Internal resistance is the opposition to current flow within a voltage source itself. All real-world power sources (batteries, generators, etc.) have some internal resistance that causes voltage drop when current flows.

2. How Does the Calculator Work?

The calculator uses the internal resistance formula:

Where:

• \( R_{int} \) — Internal resistance (ohms)
• \( V_{no\_load} \) — Voltage with no load (volts)
• \( V_{load} \) — Voltage under load (volts)
• \( I_{load} \) — Current under load (amps)

Explanation: The formula calculates the internal resistance by measuring the voltage drop from no-load to loaded condition and dividing by the load current.

3. Importance of Internal Resistance Calculation

Details: Knowing internal resistance helps determine battery health, predict voltage sag under load, design power systems, and understand source efficiency. Lower internal resistance generally indicates better performance.

4. Using the Calculator

Tips: Measure no-load voltage with source disconnected, then measure voltage and current under known load. All values must be positive, and load current must be greater than zero.

5. Frequently Asked Questions (FAQ)

Q1: Why does internal resistance matter?
A: It affects how much voltage drops when current is drawn, impacting device performance and battery life.

Q2: What are typical internal resistance values?
A: New AA batteries: 0.1-0.3 ohms, car batteries: 0.005-0.02 ohms, lithium-ion: 0.05-0.2 ohms.

Q3: How does temperature affect internal resistance?
A: Resistance generally decreases with increasing temperature in most battery types.

Q4: Can internal resistance be too low?
A: Very low internal resistance can lead to high short-circuit currents, requiring proper protection circuits.

Q5: How does internal resistance change over time?
A: Internal resistance increases as batteries age, indicating degradation and reduced capacity.