eli5 – Why is electric current a fundamental quantity but not electric charge? Can’t they both be defined in the other’s terms?
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Electric current is not a ‘fundamental quantity’. It is coloumbs per second (C/s). I am not exactly sure what you mean by fundamental quantity, could you maybe clarify?
**Edit:** *u/Target880 has informed me that my knowledge is outdated. The Coulomb is now the base unit, not the Ampere, and a bunch of other units got swapped around in 2019. [Here’s a link](https://en.wikipedia.org/wiki/2019_redefinition_of_the_SI_base_units) to an overview for people who are interested. Everything I say below was valid until 2019, so just swap the present-tense verbs out for past-tense in your head*
**Edit Again:** *I think the above might be a tiny bit wrong. As far as I can tell, the Ampere is still the base unit BUT it’s been redefined in terms of elementary charge. Kind of irrelevant though because both definitions are completely equivalent, and they actually define the Coulomb in the definition of the Ampere.*
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I’m assuming you’re talking about the fact that the Ampere is the base unit, and coulombs are defined as Ampere-seconds.
There isn’t any fundamental reason for this. It’s just easier to measure an Amp than it is a Coulomb.
For an Amp, you just take two wires, stick them next to each other, and say “1 Amp is the current required to push these two wires apart with **x** Newtons of force”. That’s easy to do. It’s pretty chill to move current through a wire. We do it every day.
On the other hand, trying to get a Coulomb of charge is a pain. There isn’t really a good way to pump so many electrons into a space that they create a (negative) Coulomb of charge, especially not back when people were first discovering and experimenting with electricity.
We *could* make the Coulomb the base unit instead, and define the Amp as 1 Coulomb/second, but it’s just easier the other way round.
Also, the power of convention is strong. We still talk about “electromotive force” and positive current “flowing” even though those are completely incorrect terms. It’s all stuff that scientists started using when they were first exploring electricity, and we’ve just stuck with it.
Can someone ELI5 OPs question for me?
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