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# Specific charge watch

1. Why is it that when calculating the specific charge of something such as an electron and a proton, the electron and the proton have the same charge? Surely if one is negative and the other is positive, their charges will oppose?

Please give examples of calculating the magnitude of charge for an electron and proton.
2. (Original post by Jackudy3)
Why is it that when calculating the specific charge of something such as an electron and a proton, the electron and the proton have the same charge? Surely if one is negative and the other is positive, their charges will oppose?

Please give examples of calculating the magnitude of charge for an electron and proton.
Is that last line the actual question you are considering? If so, the word "magnitude" is key - the question is only interested in the size of the specific charge, not whether it is positive or negative. You are correct that they have opposite signs, but I expect that the question is more interested in having you realise how much more charge there is per unit mass on an electron than on a proton (that is, the same charge but on a "smaller" thing).
3. (Original post by Pangol)
Is that last line the actual question you are considering? If so, the word "magnitude" is key - the question is only interested in the size of the specific charge, not whether it is positive or negative. You are correct that they have opposite signs, but I expect that the question is more interested in having you realise how much more charge there is per unit mass on an electron than on a proton (that is, the same charge but on a "smaller" thing).
So if I were to be working out the specific charge of say 5 electrons and 5 protons, would it be:

((1.60x10^-19)x5)+((-1.60x10^-19)x5) all over the mass of the two combined, so ((9.11x^10-31)x5)+((1.67x10-27)x5)?
4. (Original post by Jackudy3)
So if I were to be working out the specific charge of say 5 electrons and 5 protons, would it be:

((1.60x10^-19)x5)+((-1.60x10^-19)x5) all over the mass of the two combined, so ((9.11x^10-31)x5)+((1.67x10-27)x5)?
That's a fairly unusual thing to be asked. We ususally talk about the specific charge of a single thing, even if it is made from smaller pieces, so it is usually something like an electron, proton, ion, etc. There is no single object that is made from five electrons and five protons, so it would be a strange question.

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Updated: October 21, 2017
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