how to find mass of an electron
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Historically, it was done in two steps. First, the mass-to-charge ratio was calculated by JJ Thomson in 1897. By firing electrons from a cathode gun at a known velocity, through an electric field of known strength, he was able to observe how much the field deflected the beam. That allowed him to determine the mass-to-charge ratio me/Qme/Q.
More details: J. J. Thomson 1897
Then the charge was determined by Robert Millikan and Harvey Fletcher in 1897. A fine spray of oil droplets was sprayed into the electric field. Some of the droplets would pick up a few electrons, and they adjusted the field strength so that the upward force on the electron would balance the gravitational force on the droplet. They could determine the mass of the droplet from its size, and knew the gravitational force. Since the forces balanced, that determined the size of the electric force, and thus the charge of the electron.
A nifty thing to note in that experiment is that you get discrete values for the force. The droplet will pick up 1, 2, 3, or some other integer number of electrons. So you'll see that the force required to balance the droplet will be an exact multiple of some base value, rather than a continuous range of values, showing that the electric charge comes in quanta of fixed size QQ.
Since they had Thompson's number me/Qme/Q, and now they had QQ, they could quickly figure out the mass of the electron. The experiments have gotten more sophisticated since then, using a variety of other effects, but these experiments are easily replicated by undergraduate physics students.
7.6k Views · 35 Upvotes
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Jim Pivarski, Experimental Particle Physicist, PhD Cornell 2006
Answered Jul 29, 2013
At present, there is no known method to calculate the electron mass (or any other fundamental fermion--- electroweak bosons can be calculated from the Higgs vacuum expectation value). Maybe someday if details of the Higgs potential and sources of its couplings are known, it will be possible to calculate the electron mass from first principles.
3.8k Views · 3 Upvotes

Jess H. Brewer, Professor Emeritus, Dept. of Physics & Astronomy, Univ. of British Columbia
Answered Mar 29
Originally Answered: How do you find the mass of an electron?
Measure its velocity by time-of-flight methods.Measure its momentum by observing its curvature in a known magnetic field.Repeat for various different velocities and fit the result to the relativistic momentum formula.
The assumes you know its charge already; if not, you need to do the Millikan oil-drop experiment too.
2.9k Views · 74 Upvotes

Himanshu Sharma, Business Mentor. Passionate about Physics, Quantum Mechanics, Data, Love & Sex
Answered Mar 27
Originally Answered: How do you find the mass of an electron?
Following is a link to an amazingly explained solution to your problem. Please go through it if yo u are really interested.
http://www.pa.msu.edu/courses/20...
337 Views · 1 Upvote

Abhishek Goswami, Here comes the Sun.
Answered Dec 5, 2015
Originally Answered: How can I measure electron mass?
The ratio of the electron charge to its mass, e/m, can be determined from the curvature of the path of an electron in a magnetic field. That can be seen in a cathode ray tube (e.g an old tv) where the electrons are steered around with magnetic fields.
1.6k Views · 1 Upvote

Ali Abdulla, Nuclear physics and Quantum Mechanics professor
Answered Mar 28
Originally Answered: How do you find the mass of an electron?
This was done long time a go by Millikan,his famous oil drop experiment,where he measured e/m, ratio , charge/mass,then e measured in coulomb unit which is 1.6 X 10^-19 Coulomb,so m is this charge /the ration= 9.1 X 10^-31 kg.
You can find the details of the experiment in any general physics book, like Sear and Zemanisky.
More details: J. J. Thomson 1897
Then the charge was determined by Robert Millikan and Harvey Fletcher in 1897. A fine spray of oil droplets was sprayed into the electric field. Some of the droplets would pick up a few electrons, and they adjusted the field strength so that the upward force on the electron would balance the gravitational force on the droplet. They could determine the mass of the droplet from its size, and knew the gravitational force. Since the forces balanced, that determined the size of the electric force, and thus the charge of the electron.
A nifty thing to note in that experiment is that you get discrete values for the force. The droplet will pick up 1, 2, 3, or some other integer number of electrons. So you'll see that the force required to balance the droplet will be an exact multiple of some base value, rather than a continuous range of values, showing that the electric charge comes in quanta of fixed size QQ.
Since they had Thompson's number me/Qme/Q, and now they had QQ, they could quickly figure out the mass of the electron. The experiments have gotten more sophisticated since then, using a variety of other effects, but these experiments are easily replicated by undergraduate physics students.
7.6k Views · 35 Upvotes
MORE ANSWERS BELOW. RELATED QUESTIONS
What is the relative mass of an electron?
1,650 Views
What is the mass of an electron?
2,815 Views
How do you calculate the mass of a single electron?
2,366 Views
Is an electron visible or not? If not, then how do we calculate their mass?
167 Views
Do protons and electrons have the same mass?
2,774 Views
OTHER ANSWERS

Jim Pivarski, Experimental Particle Physicist, PhD Cornell 2006
Answered Jul 29, 2013
At present, there is no known method to calculate the electron mass (or any other fundamental fermion--- electroweak bosons can be calculated from the Higgs vacuum expectation value). Maybe someday if details of the Higgs potential and sources of its couplings are known, it will be possible to calculate the electron mass from first principles.
3.8k Views · 3 Upvotes

Jess H. Brewer, Professor Emeritus, Dept. of Physics & Astronomy, Univ. of British Columbia
Answered Mar 29
Originally Answered: How do you find the mass of an electron?
Measure its velocity by time-of-flight methods.Measure its momentum by observing its curvature in a known magnetic field.Repeat for various different velocities and fit the result to the relativistic momentum formula.
The assumes you know its charge already; if not, you need to do the Millikan oil-drop experiment too.
2.9k Views · 74 Upvotes

Himanshu Sharma, Business Mentor. Passionate about Physics, Quantum Mechanics, Data, Love & Sex
Answered Mar 27
Originally Answered: How do you find the mass of an electron?
Following is a link to an amazingly explained solution to your problem. Please go through it if yo u are really interested.
http://www.pa.msu.edu/courses/20...
337 Views · 1 Upvote

Abhishek Goswami, Here comes the Sun.
Answered Dec 5, 2015
Originally Answered: How can I measure electron mass?
The ratio of the electron charge to its mass, e/m, can be determined from the curvature of the path of an electron in a magnetic field. That can be seen in a cathode ray tube (e.g an old tv) where the electrons are steered around with magnetic fields.
1.6k Views · 1 Upvote

Ali Abdulla, Nuclear physics and Quantum Mechanics professor
Answered Mar 28
Originally Answered: How do you find the mass of an electron?
This was done long time a go by Millikan,his famous oil drop experiment,where he measured e/m, ratio , charge/mass,then e measured in coulomb unit which is 1.6 X 10^-19 Coulomb,so m is this charge /the ration= 9.1 X 10^-31 kg.
You can find the details of the experiment in any general physics book, like Sear and Zemanisky.
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electron mass is 9.1093856 x 10raseto the power 31
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