Electric Charge Video Lessons

Concept

# Problem: In the late 19th century, great interest was directed toward the study of electrical discharges in gases and the nature of so-called cathode rays. One remarkable series of experiments with cathode rays, conducted by J. J. Thomson around 1897, led to the discovery of the electron.With the idea that cathode rays were charged particles, Thomson used a cathode-ray tube to measure the ratio of charge to mass, q/m, of these particles, repeating the measurements with different cathode materials and different residual gases in the tube.What is the most significant conclusion that Thomson was able to draw from his measurements?(a) He found a different value of q/m for different cathode materials.(b) He found the same value of q/m for different cathode materials.(c) From measurements of q/m he was able to calculate the charge of an electron.(d) From measurements of q/m he was able to calculate the mass of an electron.

###### FREE Expert Solution

Cathode rays are streams of fast-moving electrons in discharge tubes. q is the charge of the electron and m the mass of the same.

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###### Problem Details

In the late 19th century, great interest was directed toward the study of electrical discharges in gases and the nature of so-called cathode rays. One remarkable series of experiments with cathode rays, conducted by J. J. Thomson around 1897, led to the discovery of the electron.

With the idea that cathode rays were charged particles, Thomson used a cathode-ray tube to measure the ratio of charge to mass, q/m, of these particles, repeating the measurements with different cathode materials and different residual gases in the tube.

What is the most significant conclusion that Thomson was able to draw from his measurements?

(a) He found a different value of q/m for different cathode materials.

(b) He found the same value of q/m for different cathode materials.

(c) From measurements of q/m he was able to calculate the charge of an electron.

(d) From measurements of q/m he was able to calculate the mass of an electron.