Apparatus is designed to work on mains, High voltage power supply built-in with one Analog Voltmeter is provided to measure the deflection voltage. Power supply unit provided with separate focus control , intensity control , X-shift and deflection controls knobs ,Complete unit includes fine electron beam tube (Cathode Ray tube) fitted on graduated wooden frame with scale divided in centimeters, deflecting magnetometer with permanent magnetic compass included. Compass stand, a pair of bar magnet. Complete in all respects. To determine the specific charge e/m of an electron using thompson method.