Electric current function of time

  • Thread starter Karol
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  • #1
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Homework Statement


##i=20\sin(377t)## is the current function. in the time interval 0-1/120 sec what is the charge that passed

Homework Equations


$$q=\int_0^t i dt$$

The Attempt at a Solution


$$q=\int_0^{1/120} 20\sin(377t) dt=\frac{20}{377}\int_0^{3.14} \sin x dx$$
$$q=-\frac{20}{377}\cos x|_0^{3.14}=-\frac{20}{377}(-0.0015)=79.6\cdot10^{-6}[Coulomb]$$
It should be q=0.106
 

Answers and Replies

  • #3
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One word is enough, thanks
 
  • #4
haruspex
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One word is enough, thanks
Maybe, but I'll add few anyway.
It's not a good idea to substitute numbers in prior to the final step, particularly if they're only approximations.
##\cos(\pi)## is exactly -1, and you should not be using a calculator for that.
 

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