The charge flowing through a circuit is(adsbygoogle = window.adsbygoogle || []).push({});

q(t)=[3e^(-t) - 5e^(-2t)]--------(1)

find the value of t and then current i.

as i=dq/dt.

i am doing it like this

i=-3e^-t + 10e^-2t..................taking derivative

let e^-t=u...........for eaze

i=10[u^2-3u/10]

let 1=0 then

10[u^2-3u/10]=0

10[u^2 - 2(u)(3/20) + (3/20)^2 - (3/20)^2]=0 .....using formula

10[u-3/20]^2 - 10[3/20]^2=0

10[u-3/20]^2=10[3/20]^2

10[u-3/20]^2=9/40

[u-3/20]^2=9/400

u-3/20=sqrt[9/400]

u=sqrt[9/400] + 3/20

e^-t = 3/20 + 3/20.......as u=e^-t

Taking log on both side

ln[e^-t]= ln[3/10]

-t= -1.204

-----------------|

t= 1.204 seconds |------ am i doing ok till here?

-----------------|

by putting this in equation 1 we will get the vale for charge,q.

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Current Problem

**Physics Forums | Science Articles, Homework Help, Discussion**