# Why is a charge a scalar?

1. Aug 14, 2014

### shangriphysics

Why is a charge from say an electron a scalar. It has a constant magnitude, and it has a direction.

2. Aug 14, 2014

### Vanadium 50

Staff Emeritus
In what direction do you think it points?

3. Aug 14, 2014

### haruspex

Having a sign (+/-) is not the same as having direction unless you're looking at a 1-dimensional space.

4. Aug 15, 2014

### ShayanJ

The +/- convention, is only a proper and easy to use convention!!!
Its OK to say that the two kinds of charges are black/white, fool/wise, fat/thin and any other pair of opposite nouns. The only problem is finding a way so that mathematically opposites attract and likes repel, and that's easiest when we use +/- convention, so we use it! There is nothing about direction here!

Last edited: Aug 15, 2014
5. Aug 15, 2014

### haruspex

No, it's a bit more than a convention. You can add charges, allowing charges of opposing signs to cancel appropriately. That's a genuine mathematical interpretation of the sign.

6. Aug 15, 2014

### ShayanJ

You can as well say a fool and a wise combined, make an ordinary person. Its just that the +/- convention needs no such additional weird construction.
I should add that the important role of mathematics in physics, makes the +/- convention also the most natural one, in addition to being an easy and proper one.

Last edited: Aug 15, 2014
7. Aug 15, 2014

### D H

Staff Emeritus
I suspect shangriphysics is using a dictionary definition of "scalar", such as "scalar - noun. (Mathematics, Physics). A quantity possessing only magnitude." (Source: http://dictionary.reference.com/browse/scalar).

In physics (and this is a physics question), charge is a scalar rather than a vector or a tensor. In fact, it's all three; a scalar can be viewed as a one dimensional vector or a zeroth order tensor. However, we usually don't call one dimensional vectors "vectors". We call them scalars.

8. Aug 15, 2014

### ShayanJ

I don't think that's correct because it means charge is something like a one dimensional position variable. But that's not true!
The +/- convention for electric charge is different from the +/- associated to different parts of the real line!

9. Aug 15, 2014

### D H

Staff Emeritus
Ignoring that charge is quantized, charge is exactly "something like a one dimensional position variable".

10. Aug 15, 2014

### hongiddong

Oh, I had this same question. This makes more sense now.

11. Aug 15, 2014

### shangriphysics

Thanks everyone for all your help! This is much clearer now to me!

12. Aug 16, 2014

### Shing Ernst

Now everything makes sense, I used to think (with similar reasoning) why energy can't be a vector.

Thanks, man!

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