# In which cases is it better to use Gauss' law?

I could, for example calculate the electric field near a charged rod of infinite length using the classic definition of the electric field, and integrating the: $$\overrightarrow{dE} = \frac{dq}{4 \pi \varepsilon_0r^2}\overrightarrow{a_r}$$ Right? So, why in some cases that it's possible to also use this method, do we choose Gauss' law. And moreover, from which criterion do we judge to solve with either way? I am aware of the requirements to use Gauss' law but I stil haven't understood what are the patterns I should notice that would direct me to use Gauss' law to solve a problem.

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Your average physicist is lazy. Constructively lazy, but lazy nonetheless. Constructively lazy people take the easiest way that will work... –  dmckee Aug 10 '12 at 19:36
Me too! I just still haven't figure out how exactly to recognise the easiest way, the patterns I should notice that would direct me to Gauss' law. See? I'm that lazy! :) –  Dimitris Tzortzis Aug 10 '12 at 19:38
"Constructively lazy"... I like that (although it bears remembering that it is entirely different from actual laziness). –  David Z Aug 10 '12 at 19:45