1. What is DC Motor Resistance?

DC motor resistance is the opposition to current flow in the motor's windings. It's a crucial parameter that affects motor performance, efficiency, and heat generation. The resistance can be calculated using Ohm's Law when voltage and current are known.

2. How Does the Calculator Work?

The calculator uses Ohm's Law:

Where:

• \( Voltage \) — Potential difference across the motor (Volts)
• \( Current \) — Current flowing through the motor (Amperes)
• \( Resistance \) — Resulting resistance (Ohms)

Explanation: This fundamental relationship shows that resistance equals the ratio of voltage to current in a DC circuit.

3. Importance of Resistance Calculation

Details: Knowing a motor's resistance helps in:

• Predicting current draw at different voltages
• Estimating power dissipation (I²R losses)
• Troubleshooting motor performance issues
• Designing appropriate drive circuits

4. Using the Calculator

Tips:

• Measure voltage across the motor terminals while running
• Measure current in series with the motor
• Use consistent units (Volts and Amperes)
• For accurate results, measure at operating temperature

5. Frequently Asked Questions (FAQ)

Q1: Why does motor resistance matter?
A: Resistance affects current draw, efficiency, and heat generation. Higher resistance means less current for a given voltage but more power lost as heat.

Q2: Does resistance change with temperature?
A: Yes, copper windings increase resistance by about 0.4% per °C rise. Measure at operating temperature for accurate results.

Q3: What's a typical resistance range for small DC motors?
A: Small hobby motors typically range from 1-50 ohms, while larger motors may be in the milliohm range.

Q4: Can I measure resistance directly with a multimeter?
A: Yes, but the reading may differ from operational resistance due to brush contact resistance and temperature effects.

Q5: How does resistance affect motor speed?
A: Higher resistance reduces current, which reduces torque and may lower speed under load. It also increases voltage drop across the windings.