Saturday, 5 January 2019

electromagnetism - Why does a moving charge create electricity


Now i have been studying a chapter called current electricity and i found out that moving chages can create electricity why is this possible? Is it the holes and the electrons combining together and creeating heat and light and us pecieving it as electricity? I haven't put much thought into it but i am also very impatient about knowing what it really is.



Answer



The term “electricity” doesn’t necessarily refer to any one specific thing, but rather to a whole class of phenomena related to charge, current, voltage, etc. However, it isn’t unreasonable to focus on current and say that electricity is current. So in the remainder of this answer I will talk about current.


More specifically, when a charge density, $\rho$, moves with a velocity, $\mathbf v$, there is a quantity, $\mathbf J = \rho \mathbf v$. It turns out that this quantity is very useful, so we give it a name: current density. Once you integrate the current density over the cross section of a wire you get current. So, roughly speaking moving charges don’t “create” current, they are current. It is just a matter of definition, but it is a very useful definition for studying electric circuits.


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