Crookes tube : 1.it is composed of the following parts: glass envelope, conduction track support, paddle Wheel, circular plate, support, etc. Accessory 1. Low voltage D.C. source 10-12V. 2. High voltage induction coil: Spark distance 50-80mm. 3. Voltage adjustable transformer: A.C. 220V±10V. 4. High voltage D.C. source: 250V-300v. 5. U-shape magnet: pole distance 50-70mm. 6. Connecting wires and with crocodile clips. Demonstration Environment Condition 1. Relative humidity is not greater than 80%. 2. Temperature: -10-40.