e/m

There are 2 setups for measuring e/m. Both rely on using a magnetic field to bend the trajectory of a moving charge. They have Helmholtz coils to generate the magnetic field, and a low pressure gas which glows when a beam of electrons goes through it. This is an interesting phenomenon in itself, and is the basis of a neon light for example, and is treated in the field of Plasma Physics.

The Classen method

Here is a dated procedure for this. The rheostat referred to in this document and the circuit diagram is obsolete. It was used to control the coil current (in step 1), and is on the circuit diagram on the last page. It has been replaced by a rather nice current source.

There is a video below to walk you through taking data.

Here is the (dated) procedure.

charge to mass ratio for the electron classen Kalafut.pdf

Here is the walkthrough:

The Nakamura device 

There is a video below to walk you through taking data.

Here is a procedure for this device.  

nakamuramanual-N99-B10-7350manual.pdf

Here's an excel workbook. e_m data workbookNakamura.xlsx