How did we discover the specific charge of electrons? The specific charge of an electron is -1.60 ⋅ 10^-19 C. What is the specific charge of an electron? Q = (m (drop) ⋅ g) / E = (m (drop) ⋅ g ⋅ d) / V Which equation was used to calculate the specific charge of an electron? Today, we know that the proton-electron mass ratio is mp/me = 1836.15, which sheds light on the roles of subatomic particles and how much of the atom's mass they comprise. The discovery of the proton and the neutron further enhanced this understanding. Understanding the specific charge of an electron and its mass helped in comprehending the structure of an atom. The experiment not only determined the specific charge of an electron but also its mass. The experiment involved placing two horizontal metal plates on top of each other with an insulating substance between them, pierced with four holes. Robert Millikan and Harvey Fletcher conducted the oil-drop experiment in 1909 to determine a single electron's specific charge. The specific charge of an electron is 1.6⋅10 ^-19. (Electrons being the first subatomic particles to be discovered.) With the determination of the specific charge of an electron, the existence of subatomic particles was universally accepted. Since the charge of an electron is related to its mass, determining the specific charge of an electron also meant that the mass of an electron was determined. Let's have a look at the role this discovery played. The importance of the specific charge of an electronĭetermining the specific charge of an electron is one of the turning points in physics, which led to several new discoveries. Millikan had measured the charge of the electron qe to an accuracy of 1 percent and had raised it by a factor of 10 to a value of -1.60⋅10^-19 C within a few years. V is the voltage that holds the drop stationary. The charge of the electron may be estimated using the rearranged equation below after the mass of the drop is known. d is the distance between the plates in meters. Since we know that the voltage (V) was adjusted to balance the forces on the drop, and the electric field (E) was a product of the voltage applied, we can show it with the equation below. The mass of the drop was determined by how rapidly it descended when the voltage was turned off. This also meant that the drop was allowed to fall at its terminal velocity (v) when the voltage source was turned off. Qe is the charge of the electron in CoulombsĮ is the electric field in Newton/Coulomb G is the gravitational constant, 9.8 m/s^2 at Earth's surface An ionising radiation source, like an X-ray tube, could also be used to charge the droplets.Ī simplified diagram of Millikan's oil-drop experiment Some were charged due to friction from the nozzle when they were sprayed. A potential difference was applied across the plates to create a uniform electric field. The insulator had three holes for light to enter and one for examination. In Millikan's experiment, two metal plates were stacked on top of each other with an insulating material in between. Today, it is known as Millikan's experiment. In 1909, Robert Millikan and Harvey Fletcher conducted 'the oil-drop experiment' to determine the specific charge of a single electron. These results were important, but not enough to explain the photoelectric effect. Other scientists like George FitzGerald and Walter Kaufmann also experimented with electricity and magnetism, but only found that a charge is a continuous variable. However, he could not determine the exact charge of a single electron. JJ Thomson made progress by measuring the ratio between an electron's charge and its mass (qe / me), and estimating an electron's mass to be about 5.56 ⋅ 10 ^-4 times that of a hydrogen atom. JJ Thomson working on his experiment with cathode rays
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