Uploaded March 2026 | Updated September 2026, 3 weeks ago
Crookes Railway or Tramline tube invented in the 1800s by William Crookes it was thought to show that cathode rays had momentum. While that may be true to some extent, they don’t have enough momentum to move the paddle wheel along the tube as show here. It was later understood the movement is caused by the much heavier charged ions in the tube due to the vacuum being imperfect. This tube has fluorescent paint at the mica wheel blade tips and this is glowing under the electron bombardment. This old tube and has quite a high vacuum, so is shown here operating with 30kV between the two electrode cups. At this potential the tube does emit some x-rays so is rarely demonstrated and probably not really suitable for public or school demonstrations.
Crookes Railway or Tramline tube invented in the 1800s by William Crookes it was thought to show that cathode rays had momentum. While that may be true to some extent, they don’t have enough momentum to move the paddle wheel along the tube as show here. It was later understood the movement is caused by the much heavier charged ions in the tube due to the vacuum being imperfect. This tube has fluorescent paint at the mica wheel blade tips and this is glowing under the electron bombardment. This old tube and has quite a high vacuum, so is shown here operating with 30kV between the two electrode cups. At this potential the tube does emit some x-rays so is rarely demonstrated and probably not really suitable for public or school demonstrations.
