The experiment that proved electrons to compose current

In summary, the Tolman-Stewart experiment of 1916 provided the first direct evidence that electrons, not protons, are the charge carriers in metals. By accelerating a metal rod, they found that the inertia of the charge carriers caused them to be "thrown" to the rear surface of the rod, resulting in a negative charge. This experiment also suggests that a p-type semiconductor would not have been a suitable material for this test.
  • #1
hbweb500
41
1
I remember reading somewhere that it was discovered that electrons, not protons, composed current when an accelerated conductor was found to have slightly negative charge on the end opposite the direction of the acceleration. Because of this it was determined that electrons were free to move in conductors, not protons, and electrons were what composed current.

I can't find the name of this experiment, does anyone remember?
 
Physics news on Phys.org
  • #2
Never heard of it. I think the properties of cathode rays (electrons) seems to have determined that charge carriers were negatively charged.
 
  • #3
The Hall effect shows that the current carriers are negative.
 
  • #4
True and true, but I managed to find the text I was looking for, and it was called the Tolman-Stewart experiment. From Knight's "Physics for Scientists and Engineers, Volume 4":

"The Tolman-Stewart experiment of 1916 was the first direct evidence that electrons are the charge carriers in metals. Tolman and Stewart caused a metal rod to accelerate very rapidly. The inertia of the charge carriers within the metal (and Newton's first law) causes them to be "thrown" to the rear surface of the metal rod as it accelerates away...Tolman and Stewart found that the rear surface of a metal rod becomes negatively charged as it accelerates."
 
  • #5
Cool, hbweb. I wonder how a P-type semiconductor would measure.
 
  • #6
I don't know much about p-type semiconductors, but from what I have read a positive "hole" is created when an electron is accepted by the impurity. If all of the electrons are shoved to the back of the rod when it is accelerated, then all of the positive holes should be created back there, and thus the end should test positive...

I guess it was for the better that Tolman and Stewart didn't use a p-type when they did their test.
 

What is the experiment that proved electrons to compose current?

The experiment that proved electrons to compose current is called the cathode ray tube experiment, conducted by J.J. Thomson in 1897.

How was the cathode ray tube experiment conducted?

In the experiment, Thomson used a cathode ray tube, which is a sealed glass tube with metal electrodes at either end. He applied high voltage to the electrodes, causing a beam of electrons to travel from the negative electrode (cathode) to the positive electrode (anode).

What were the results of the cathode ray tube experiment?

Thomson observed that the beam of electrons was deflected by a magnetic field, indicating that they had a negative charge. He also measured the ratio of the charge of an electron to its mass, which was much smaller than that of an atom. This led to the conclusion that electrons were the fundamental particles of electricity and were responsible for the flow of current.

How did the cathode ray tube experiment impact our understanding of electricity?

The cathode ray tube experiment provided evidence for the existence of electrons and their role in electrical current. This led to a better understanding of electricity and the development of modern electronics, including the invention of the television and computer screens.

Are there any other experiments that have contributed to our understanding of electrons composing current?

Yes, there have been numerous experiments that have further confirmed the role of electrons in current, including the Millikan oil drop experiment and the electron diffraction experiment. These experiments have also helped us understand the properties and behavior of electrons in more detail.

Similar threads

  • Electromagnetism
Replies
7
Views
888
  • Electromagnetism
Replies
17
Views
1K
Replies
8
Views
7K
Replies
14
Views
2K
  • Electromagnetism
2
Replies
36
Views
2K
Replies
21
Views
2K
Replies
3
Views
378
Replies
25
Views
2K
Replies
61
Views
2K
  • Electromagnetism
Replies
2
Views
10K
Back
Top