# Controls

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

## Task: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.
$${r = \frac {m_e\cdot v_0}{e\cdot B}}=4.25\,\rm{cm}$$