Demonstrates the motion of electrons in a magnetic field, and determines the charge-to-mass ratio of an electron (e/m). Accelerating voltage is continuously variable between 0 and 250V, and polarity of voltage on deflection plates and polarity of electromagnet can both be reverted. Lorentz tube is 180 degrees rotatable. Comes with built-in power supply, instruction manual and wooden storage case. Acceleration Voltage : 0~250V. Voltage Meter Deviation : ≤2.5%. Magnetization Current : 0~2.5A. Current Meter Deviation: ≤2.5%.