# Local and integral physical quantities

cseil
Hello everyone,
I'd like to know if my understanding of local and integral quantities is clear.

An integral quantity refers to the entire physical system, it is not defined point by point.
A local one is defined point by point, for example ρ(x,y,z).

Can I consider the charge dq as a local quantity? It is the charge of an infinitesimal element of something.
I can integrate it and find the integral quantity q.

In some quizzes my prof asks to write three or four local and integral quantities.
Integral quantities could be mass, electric potential, resistance, charge.
Local quantities could be resistivity, electric field, density or the density of current.

I'm not sure if I can consider local quantities the differential quantities like dL, dm, dq, di, dV. The correspondent integral ones are lenght, mass, charge, intensity of current, potential.

## Answers and Replies

cseil
Are you asking in the context of continuity equations?
Anyway, you want to start by stating the text-book definition of the terms you are trying to understand.

http://help.howproblemsolution.com/959914/local-and-integral-physical-quantities

It is not asked there. It's my post here reported on that website, I didn't even know it existed!
There's no definition on the textbook, sometimes it just refers to them.

Homework Helper
What is the context?