Electric Field linearly accelerates $e^{-}$ from voltage in Electron Gun: Va
Magnetic Field circularly accelerates $e^{-}$ from current in Helmholtz coils through coils: Iα

Schematic Diagram

Schematic layout of the experiment about electron deflection in a magnetic field

Check the validity of the formula ${r=\frac{m_e\cdot v_0}{e\cdot B}}$ for the radius of the circular path using the experiment.

The theoretical circular path is shown in blue and can be switched on and off.
$F_{Zentripetal} = m_e\frac{{v_0}^2}{r} $ $$ F_{Lorentz} = e\cdot v_0 \cdot B$$
Picture of the real experiment for deflection of electrons in a magnetic field
Grid for data logging
r =

Useable Variables:

m  = mass of an electron
e  = charge of an electron
v0 = velocity of the electron
B  = strength of magnetic field

Typing tip:

x² must be typed as x*x