Find the charge q(t) flowing through a device if the current is: (a) i(t)=3A, q(0)=1C, (b) i(t)=(2t+5) mA, q(0)=0 (c) i(t)=20 cos(10t+\pi/6) \mu A, q(0)=2 \muC (d) i(t)= 10 e ^-30t \sin 40tA, q(0)=0

alan3885uo

alan3885uo

Open question

2022-08-20

Find the charge q(t) flowing through a device if the current is: 

(a) i(t)=3A, q(0)=1C, 

(b) i(t)=(2t+5)mA, q(0)=0 

(c) i(t)=20cos(10t+π/6)μA, q(0)=2μC 

(d) i(t)=10e-30tsin40tA, q(0)=0

Answer & Explanation

etapi9a

etapi9a

Beginner2022-08-21Added 12 answers

Step 1
The givens and requirements:
It is required to obtain the charge q(t) flowing through a device, given that the current is:
(a) i(t)=3A,q(0)=1C
(b) i(t)=(2t+5)mA,q(0)=0
(c) i(t)=20cos(10t+π6)μA,q(0)=2μC
(d) i(t)=10e30tsin40tA,q(0)=0
Step 2
Mathematically, the relationship between current ii, charge q, and time t is
i(t)=dq(t)dt
By integrating both sides of the previous equation, we obtain
q(t)=q(0)+0ti(τ)dτ
(a)
q(t)=q(0)+0ti(τ)dτ
=1+0t3dτ
=1+(3τ){}{0}t
=(1+3t)C
To check:
PSKq(t)=1+3task
=1+30
=1C
cronaficsiiilm

cronaficsiiilm

Beginner2022-08-22Added 1 answers

Step 4
(b)
q(t)=q(0)+0ti(τ)dτ
=0+0t(2τ+5)dτ
=(2τ22+5t){0}t
=(t2+5t)mC
To check:
q(0)=t2+5t
=02+50
=0

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