# find the charge q(t) flowing thru a device if the current is:

• Dec 22nd 2010, 02:37 PM
bigwave
find the charge q(t) flowing thru a device if the current is:
$\displaystyle A=$Amperage $\displaystyle C=$Coulombs

$\displaystyle i(t)= 3A$, $\displaystyle q(0) = 1C$

The Ans is $\displaystyle 3t+1$

this is very new subject to me but I assume we want to use

$\displaystyle Q \triangleq \int_{t_0}^t i \ dt$
• Dec 22nd 2010, 03:07 PM
Quote:

Originally Posted by bigwave
$\displaystyle A=$Amperage $\displaystyle C=$Coulombs

$\displaystyle i(t)= 3A$, $\displaystyle q(0) = 1C$

The Ans is $\displaystyle 3t+1$

this is very new subject to me but I assume we want to use

$\displaystyle Q \triangleq \int_{t_0}^t i \ dt$

Yes,

$\displaystyle \displaystyle\ i=\frac{dQ}{dt}\Rightarrow\ Q=\int{i}dt$

$\displaystyle \displaystyle\int{i}dt=Q=it+q(0)$

where $\displaystyle q(0)$ is the initial charge.
• Dec 22nd 2010, 03:20 PM
bigwave
then we just plug
so for

$\displaystyle \int{i}dt=Q=it+q(0)$

then we just plug in $\displaystyle 3$ into $\displaystyle it$ and $\displaystyle 1C$ into the q(0)

to get the $\displaystyle 3t + 1C$
• Dec 22nd 2010, 03:37 PM