1. What is Motor Resistance?

The resistance of a brushed DC motor is a fundamental electrical characteristic that determines how much current the motor will draw at a given voltage. It's crucial for understanding motor performance and thermal characteristics.

2. How Does the Calculator Work?

The calculator uses Ohm's Law:

Where:

• \( R \) — Resistance in ohms (Ω)
• \( V \) — Voltage in volts (V)
• \( I \) — Current in amperes (A)

Explanation: The resistance is calculated by dividing the voltage applied to the motor by the current it draws.

3. Importance of Resistance Calculation

Details: Knowing the motor's resistance helps in:

• Predicting current draw at different voltages
• Calculating power dissipation (I²R losses)
• Designing appropriate motor drivers and protection circuits
• Troubleshooting motor performance issues

4. Using the Calculator

Tips:

• Measure voltage across motor terminals while running
• Measure current in series with the motor
• For most accurate results, measure at steady-state operating conditions
• Values must be positive (voltage > 0, current > 0)

5. Frequently Asked Questions (FAQ)

Q1: Why does motor resistance matter?
A: Resistance determines current draw, power losses, and heating in the motor windings.

Q2: Does resistance change with temperature?
A: Yes, copper windings have about 0.4% resistance increase per °C temperature rise.

Q3: How does this differ from stall current measurement?
A: Stall current includes back-EMF effects, while this calculation gives the pure winding resistance.

Q4: 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.

Q5: Can I use this for brushless motors?
A: No, brushless motors have more complex impedance characteristics that vary with speed.