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Specific charge question

When we work out specific charge, do we take the charge to be positive? In my textbook, it says that the specific charge of the electron is positive, which wouldn't be true if we used its charge to be

-1.6 \times 10^-19

, would it?

Thanks

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(edited 9 years ago)

Reply 1

crashMATHS

Original post by AlphaNick

Yes, it's supposed to be negative, -1.60x10^-19

Why does the AQA book say that the specific charge of an electron is 1.76 x 10^11 then? I came to the assumption that the formula for specific charge was hence:

specific charge = | \frac{charge}{mass} |

?

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(edited 9 years ago)

Reply 2

Stonebridge

It can be expressed as either positive or negative. Look through various books and sources and you will find both.
In many cases the sign of the charge is not important. What is important is the magnitude of the ratio.
If you see the specific charge of an electron quoted as 1.76 x 10¹¹Ckg^-1 then there is no need to worry about it. You know the charge is negative and the value quoted is just the magnitude of the ratio. If in doubt, when you give the value, put the minus sign in.

Reply 3

crashMATHS

Original post by AlphaNick

because it's wrong, the electron's specific charge is -1.76x10¹¹C kg^-1

Yeah, I agree. I don't like the fact that AQA are explicitly telling incorrect things. They should at least say: 'the magnitude of the specific charge of an electron is...'

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