Timeline for Electric current notation
Current License: CC BY-SA 3.0
13 events
| when toggle format | what | by | license | comment | |
|---|---|---|---|---|---|
| May 3, 2015 at 18:02 | comment | added | mwa1 | "Which sources" : different textbooks, the internet, teachers | |
| May 2, 2015 at 16:42 | comment | added | Qmechanic♦ | $\uparrow$ Which sources? | |
| May 2, 2015 at 12:14 | comment | added | Kyle Kanos | For more on the differences of derivatives/differentials, see this Physics.SE post | |
| May 2, 2015 at 11:11 | review | Close votes | |||
| May 3, 2015 at 4:31 | |||||
| May 1, 2015 at 17:03 | answer | added | slhulk | timeline score: 1 | |
| May 1, 2015 at 16:54 | comment | added | Demosthene | Then I'd say the following: $\frac{dq}{dt}$ is the total derivative of $q(t)$, $\frac{\partial q}{\partial t}$ is the partial derivative of $q(t,x_1,x_2,\ldots)$ (some function of $t$ and something else); $\Delta q$ is a large/macroscopic variation of $q$, whereas $dq$ is its infinitesimal counterpart, and finally $\delta q$ is somewhere in between, i.e. it is not necessarily infinitesimal. You'll find this $\delta$ symbol frequently in the calculus of variation - $\delta q$ is precisely a variation in $q$. | |
| May 1, 2015 at 16:03 | comment | added | mwa1 | Absolutely, it reads $I = \frac{\delta q}{\delta t}$ and is defined as " the quantity of charge $\delta q $ going through the section of a conductor between $t$ and $t+\delta t$ " | |
| May 1, 2015 at 15:54 | comment | added | Demosthene | Are you sure it's $\delta q$ and not $\partial q$? | |
| May 1, 2015 at 15:50 | comment | added | mwa1 | "What is confusing about that" : Mostly the inconsistency of notations across different sources. As I said, I just saw the current defined as $I = \frac{\delta q}{\delta t}$ (and it was the first time I had ever seen $\delta t$). | |
| May 1, 2015 at 15:11 | comment | added | ACuriousMind♦ | Work is defined as a line integral $W := \int_\gamma F$, this only is the same as $F = \mathrm{d}W/\mathrm{d}x$ if the line integral does not depend on the path taken, but onyl on the endpoints. Current, on the other hand, is defined as $I := \mathrm{d}q/\mathrm{d}t$. What is confusing about that? | |
| May 1, 2015 at 14:56 | comment | added | mwa1 | I'm not sure I understand it myself, I find this confusing. As I understand it, I can only write $dq = I dt$ if $I = \frac{dq}{dt}$. But how do I know this ? is it only by definition ?(it looks like a chicken and egg problem). Then why can't I write $F = \frac{dW}{dx}$ for the work of a force? | |
| May 1, 2015 at 14:20 | comment | added | ACuriousMind♦ | Uh...you can write $\mathrm{d}\omega$ for any differential form $\omega$. Exactness would mean $\mathrm{d}\eta = \omega$ for some $\eta$. I don't understand your question. | |
| May 1, 2015 at 14:16 | history | asked | mwa1 | CC BY-SA 3.0 |