Who determined the ratio of charge (e) of an electron to its mass(m) ?

The ratio of charge (e) of an electron to its mass (m) was determined by J.J. Thomson in 1897 through his cathode ray experiment. Here are the steps he took:

1. Thomson constructed a cathode ray tube, which is a vacuum-sealed glass tube with metal electrodes at each end. When a high voltage is applied across the electrodes, a beam of particles (cathode rays) travels from the negative electrode (cathode) to the positive electrode (anode).

2. He then applied a magnetic field to the cathode ray tube, which caused the cathode rays to deflect. By adjusting the strength of the magnetic field and observing the amount of deflection, Thomson was able to calculate the velocity of the cathode rays.

3. Thomson also applied an electric field in addition to the magnetic field. The electric field caused the cathode rays to deflect in the opposite direction to the magnetic field. By balancing the two fields, Thomson was able to make the cathode rays travel in a straight line again.

4. By knowing the velocity of the cathode rays and the strength of the electric field, Thomson was able to calculate the charge-to-mass ratio (e/m) of the cathode rays.

5. Thomson concluded that the cathode rays were made up of particles that were much smaller and lighter than atoms. He called these particles 'corpuscles', but they are now known as electrons.

6. The value of e/m for electrons determined by Thomson is approximately 1.76 x 10^11 coulombs per kilogram. This was the first time that the properties of subatomic particles had been measured.