Notation clarification

  • Thread starter rambo5330
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  • #1
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I'm taking a calculus based physics class this year and I've had a few issues getting reliable information on the following notation


the following equation I = [tex]\frac{dQ}{dt}[/tex]

the previous equatin represents the instantaneous current in a conductor.

what exactly is the term dQ or dt saying. in calculus if i see [tex]\frac{dy}{dx}[/tex]

I know it means take the derivative of this with respect to x.
now from my understanding d is like delta but where as delta may deal with rather large changes etc d represents an infinitly small piece of something i.e. an infinitely small charge over and infinitely small time? is that what that is saying

and whatever meaning it does have is it related completely to calculus itself or is this a physics definition?

thank you...
 

Answers and Replies

  • #2
The actual derivative (dy/dx) is just equal to the:

Limx-Inf f(x+delta x) - f(x)all over delta x

It is called the limit definition of the derivative, and it is a calculus definition that can be used both in physics and calculus. It isn't used in solely one or the other
 
  • #3
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I understand that part, its the actual meaning of the symbol dQ... or dx for that matter that im looking for

what im finding so far is that dQ could mean an infinitly small portion of a larger charge Q
 
  • #4
verty
Homework Helper
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Officially, dq is part of a larger complex and the meaning is given by the context. It doesn't have a meaning by itself. But I like to think of it as a really small change of the variable. You might think of dQ/dt as "the ratio of really small changes of Q and t".
 

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