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If the switch is closed at t = 0, find the

current in the inductor at t = 0.224 s. Answer

in units of A.

&

Find the current in the switch at that same

time.

I know that i must use i = V/R(1 - e^-t/L/R) but cant seem to get the right answer.

Any help is appreciated

................5 ohms

-------------^^^^^^^------I

I........................................I

I.......10 ohms............1.4 H...I

I------^^^^^^^^---&&&&--I

I........................................I

I.......S.........30 V.....5 ohms.I

I-------/..---I I----^^^^^--I

What am I doing wrong?

i = V/R(1 - e^-t/L/R)

i = V/R(1 - e^-t/L/R + V/5 = (30 - V)/5

(V/10)( 1 - e^-(0.224*10/1.4) + V/5 = -V/5 + 6

0.1V(0.798)+0.4V = 6

(0.4+0.0798)V = 6

V = 6/0.4798 = 12.5 v

The inductor current at t = 0.224 s

i = V/R(1 - e^-t/L/R)

i = (12.5/10)[ 1 - e^-(0.224(10/1.4) ]

i = 0.9976 A

The switch current:

Is = i + V/5 = 0.9976 + 12.5/5 = 3.497 A

current in the inductor at t = 0.224 s. Answer

in units of A.

&

Find the current in the switch at that same

time.

I know that i must use i = V/R(1 - e^-t/L/R) but cant seem to get the right answer.

Any help is appreciated

................5 ohms

-------------^^^^^^^------I

I........................................I

I.......10 ohms............1.4 H...I

I------^^^^^^^^---&&&&--I

I........................................I

I.......S.........30 V.....5 ohms.I

I-------/..---I I----^^^^^--I

## Homework Statement

What am I doing wrong?

## Homework Equations

i = V/R(1 - e^-t/L/R)

## The Attempt at a Solution

i = V/R(1 - e^-t/L/R + V/5 = (30 - V)/5

(V/10)( 1 - e^-(0.224*10/1.4) + V/5 = -V/5 + 6

0.1V(0.798)+0.4V = 6

(0.4+0.0798)V = 6

V = 6/0.4798 = 12.5 v

The inductor current at t = 0.224 s

i = V/R(1 - e^-t/L/R)

i = (12.5/10)[ 1 - e^-(0.224(10/1.4) ]

i = 0.9976 A

The switch current:

Is = i + V/5 = 0.9976 + 12.5/5 = 3.497 A

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