Quick Answer

A Crookes radiometer that isn't spinning usually needs more intense light or a gentle nudge to overcome static friction. Check the light source first, then inspect for physical obstructions.

Why Your Radiometer Might Not Spin

The Crookes radiometer, or light mill, relies on a partial vacuum inside its glass bulb. The vanes spin when light heats the darker side, creating a temperature difference that moves the air molecules. If the bulb is damaged or the vacuum is lost, the device won't work at all. Also, static electricity or dust on the vanes can cause sticking.

Troubleshooting Steps for a Stuck Radiometer

  • Check the Light Source: Place the radiometer in direct sunlight or under a strong incandescent or halogen bulb. LED and fluorescent lights often lack the intensity and heat needed to spin the vanes. If it spins in sunlight but not indoors, your light source is too weak.
  • Inspect for Physical Obstructions: Gently tilt and rotate the glass bulb. Look for any dust, debris, or a loose vane that might be blocking movement. Do not open the bulb. If you see debris inside, the vacuum is likely broken and the radiometer is beyond simple repair.
  • Give It a Gentle Start: Lightly tap the glass with your finger or gently shake the base to overcome static friction. If the vanes start moving, they should continue as long as light is present. If tapping doesn't help and the light is strong, the vacuum may be compromised.
  • Evaluate the Vacuum Seal: Hold the radiometer up to a bright light and look for any cracks or chips in the glass. A hissing sound when moved from a warm to cool area also indicates a leak. A broken vacuum means the radiometer cannot be repaired and should be replaced.

Products That Can Help

  • Crookes Radiometer Mini: Our miniature Crookes radiometer is designed for portability, so you can test it in different light conditions. If your current radiometer is stuck, trying a smaller model in a brighter spot can confirm whether the issue is light intensity or the device itself.

    Crookes Radiometer Mini

    Crookes Radiometer Mini

  • Crookes Radiometer Orange: The orange Crookes radiometer is a modern and colorful version of the original solar energy measuring instrument. If your radiometer isn't spinning, the colored glass might reduce light transmission; ensure you're using direct sunlight, not indoor lighting.

    Crookes Radiometer Orange

    Crookes Radiometer Orange