Millikan was able to calculate the charge on an electron.Oil is squirted through a hole in a metal plate. The tiny droplets are examined through a microscope.
The magnitude and direction of the p.d. is adjusted so that it is held suspended by equal and opposite forces.F = QV/dandF = mg.The power supply is switched off allowing the drop to fall and reach terminal velocity.By timing the drop over a marked distance and knowing the viscosity of air and the density of the oil drop, the radius of the drop and therefore the mass of the drop can be calculated.q = mgd /V
The magnitude and direction of the p.d. is adjusted so that it is held suspended by equal and opposite forces.F = QV/dandF = mg.The power supply is switched off allowing the drop to fall and reach terminal velocity.By timing the drop over a marked distance and knowing the viscosity of air and the density of the oil drop, the radius of the drop and therefore the mass of the drop can be calculated.q = mgd /V