The elementary charge e (the magnitude of charge carried by the electron) was determined in what is known as "Millikan's oil drop experiment", in an apparatus schematically shown below. several thousand volts cover oil spray Hint microscope A mist of oil is sprayed into a chamber, and the mass of the oil drop is determined by measuring the size of the drop and its terminal velocity (read more about it on the Wikipedia page). Because of the friction with the nozzle when the oil is aerosolized, some of the oil drops are electrically charged, and by applying an electric field between two conducting plates to suspend these oil drops, the charge on the oil drops can be determined. uniform electric field The elementary charge is the smallest unit of charge observed; all other charges on oil drops come as an integer multiple of this elementary charge, e = 1.602 x 10 C. -19 Electric field of If an oil drop of mass m = 4 x 10-15 kg carries a charge of 4e, what magnitude of electric field needs to be applied to suspend this oil drop between the two conducting plates? N/C needs to be applied. (As an aside, electric fields of 10 N/C to 10 MN/C are experimentally easy to set up-not too small to be able to set up accurately, and not too large to run into experimental difficulties.)

The elementary charge e (the magnitude of charge carried by the electron) was determined in what is known as "Millikan's oil drop experiment", in an apparatus schematically shown below. several thousand volts cover oil spray Hint microscope A mist of oil is sprayed into a chamber, and the mass of the oil drop is determined by measuring the size of the drop and its terminal velocity (read more about it on the Wikipedia page). Because of the friction with the nozzle when the oil is aerosolized, some of the oil drops are electrically charged, and by applying an electric field between two conducting plates to suspend these oil drops, the charge on the oil drops can be determined. uniform electric field The elementary charge is the smallest unit of charge observed; all other charges on oil drops come as an integer multiple of this elementary charge, e = 1.602 x 10 C. -19 Electric field of If an oil drop of mass m = 4 x 10-15 kg carries a charge of 4e, what magnitude of electric field needs to be applied to suspend this oil drop between the two conducting plates? N/C needs to be applied. (As an aside, electric fields of 10 N/C to 10 MN/C are experimentally easy to set up-not too small to be able to set up accurately, and not too large to run into experimental difficulties.)