Lag1989 problem number 12.48

The electrodes of a two-electrode lamp (diode) have the form of a thread with a radius of 0.1 mm (cathode) and a coaxial cylinder with a radius of 2.72 mm (anode). Voltage U = 100 V is applied to the electrodes. Find the force that an electron will experience when it is at a point 1 mm away from the cathode axis.