Electrons are negative.

Proof:
http://en.wikipedia.org/wiki/Hall_effect

Proof you can see:
http://en.wikipedia.org/wiki/Hall_effect_thruster

 

I think we are getting away from the T&S experiment.

Firstly @debjit625

Polarity in electricity (positive and negative) is not the same as positive and negative numbers in mathematics.

It was realised long ago that there are two polarities in electricity. They could have been named james and john but it was decided to call one terminal of the Leyden Jar positive and the other negative, for the purpose of distinction.

This is our standard and definition.

Now look at my sketch of the T&S experiment.

A piece of metal is moving with high velocity in the direction shown (actually it is spinning on the edge of a disc).

Two slip rings are connected at A and B.

The motion is suddenly arrested and the galvanometer connected to the slip rings shows a kick deflection in a certain direction.

If A and B are disconnected from the slip rings and then connected to the terminals of a Leyden Jar, the galvanometer will again show a kick deflection.

If the deflection is in the same direction as before then I can deduce that the polarity of A and B are the same in both cases.

It turns out that the direction corresponds to charge carriers moving from what we called negative on the Leyden Jar to positive.

But the magic of this experiment is that there is no (external) source of electricity.
The charge carriers within the metal are initially moving as part of the metal with no current flowing or pd observable.
When the arrrest comes the bulk matrix of the metal halts, but the charge carriers, being more mobile, continue in motion from A towards B so we know which direction they are travelling.

At bit more measurement and we can relate the mechanical work done in stopping the system to the electrical charge or pd generated.

This is what makes this experiment so remarkable.

The experiment is similar to saying I can 'prove' a brick is 9 inches long by measuring it against a 12 inch ruler. It is comparison with a standard. Not a mathematical type proof.

 

I think we are getting away from the T&S experiment.

I think the question was not about T&S experiment.Your question was

So suppose you were asked to provide a practical demonstration to prove, and preferably measure, that the carriers of current in a metal are negatively charged how would you do this?

It should be kind of like this ...

So suppose you were asked to provide a practical demonstration to prove, and preferably measure, that the carriers of current in a metal are electrons how would you do this ,without any use of external power source?

Polarity in electricity (positive and negative) is not the same as positive and negative numbers in mathematics.

No they are same,but if you are talking about the process of comparison between two charges in mathematics we call it RELATIONS.

It was realised long ago that there are two polarities in electricity. They could have been named james and john but it was decided to call one terminal of the Leyden Jar positive and the other negative, for the purpose of distinction.

Yes thats what I am trying to say. It was realized or assumed ,so if that’s the case,
then by the facts assumed and without using any external source there are proves given on first post “Photo electric effect” and also some more like “Thermo-couple” , “Volta effect”.

 

Yes thats what I am trying to say. It was realized or assumed

Your English is very good, however I know nothing about you, so I can't tell if this statement is an issue of language or something else.

You do seem to like flatly contradicting my statements, without any word of explanation or support.

There is a huge difference between realized and assumed both in English and formal science. Which do you mean as the use of one or the other totally changes the meaning of your words?

No they are same,but

I said, and I meant they are different.
Here we have another unsupported flat contradiction.

Since you seem to have some facility with electronics and mathematics, how about displaying a calculation of what happens when the Hall effect is applied to a current the could be holes moving one way or electrons moving the other? It is a simple piece of vector mechanics to show that both holes and electrons are deflected in the same direction, but the resultant polarity could be positive or negative. No set of positive and negative numbers displays this behaviour, to my knowledge.

 

There is a huge difference between realized and assumed both in English and formal science. Which do you mean as the use of one or the other totally changes the meaning of your words?

The same thing goes for you also,In your question you asked to prove something then when " beenthere " gave the example of vacuum tube rectifier ,you said it is using a external current source ......... so it is not proving the stuff and at last you came up with your T&S experiment (which is the only prove we have in this world isnt ????).
But your experiment didnt proved that electrons are negatively charged,and when I asked you about this, your answer was

It was realised long ago that there are two polarities in electricity.

So this is the way you prove by realising.

So if the realised stuff works in your process of proving this thing, then what is the problem with the post of other members more likely "beenthere's" post.

It was realized or assumed

I said it literally.

The way you proved was not wrong ,it is the way to do this but your question was not right.

Keep posting

 

Since this is my thread I'll decide what question to ask. There was a good reason for not being too specific.

Anyway since you don't want to present the calculation I called for, here it is.