What is the value of v0(t) for the circuit shown in the figure, assuming zero initial conditions?

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UPSC ESE (Prelims) Electronics and Telecommunication Engineering 19 Feb 2023 Official Paper
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  1. vo(t) = 40(1 - e+ 2te-t)u(t) V
  2. vo(t) = 40(1 - e-2t - 2te-2t)u(t) V
  3. vo(t) = 40(1 - e-t - 2te-2t)u(t) V 
  4. vo(t) = 40(1 - e-2t + 2te-t)u(t) V

Answer (Detailed Solution Below)

Option 2 : vo(t) = 40(1 - e-2t - 2te-2t)u(t) V
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ST 1: UPSC ESE (IES) Civil - Building Materials
20 Qs. 40 Marks 24 Mins

Detailed Solution

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Given that, R=, L = 1H, C = 

The response for a series RLC circuit with source will be, V(t) = Vss + (A1 + A2t)e-at for a = W0.

 a = = 2

0 =  = = 2.

a = ; system is critically damped.

At t = ; inductor is short circuit and capacitor is open circuit.

V(t) = Vss + (A1 + A2t)e-at

= 40 + A1e-2t + A2te-2t

At t = 0, voltage across capacitor is zero V(t) = 0.

 0 = 40 + A1e-2 + A2te-2

 A1 + A2 = -40

= 0 + -2 A1e-2t - 2A2te-2t + A2e-2t

0 = -2 (-40) - 0 + A2

 A= -80

Here, option 2 is correct.

 

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