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Given the Laplace Transform, find the circuit

The Laplace Transform of the current in a certain series circuit is:

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Invert the Laplace Transform to find the expresion for the current I(t), not by partial fraction expansion, but by completing the square in the denominator, dividing the expression for tex2html_wrap_inline263 in two and using two entries from your table of Laplace Transforms.

What was the circuit and the input voltage in this case ?

SOLUTION :

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Using:

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with a=1 and tex2html_wrap_inline267 :

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To find a circuit this might represent, multiply out the fraction in the Laplace Transform:

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The reason for dividing by s was to give the LHS the form of the Laplace Transform of a series LRC circuit:

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So the series LRC circuit would have the component values L=1henry , R=2ohm and C=0.2farad.

Then the RHS is the Laplace Transform of the input voltage.

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So the input voltage is a 7volt step function plus a unit delta function (at t=0).



Keith Jones
Mon Jun 25 11:57:27 EST 2001