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Network Elements and the Concept of Circuit

  1. The initial voltage on the capacitor is Vc (0) = 2 V, I (s) = u (t) cos t find V (t) for t > 0—


    1. V (t) =
      1
      cos (t – 45º) +
      3
      e– t
      22
    2. V (t) = 2 cos (t – 45º) +
      3
      e+ t
      2
    3. V (t) = cos (t – 45º) +
      1
      e– 2t
      2
    4. V (t) = cos (t + 45º) +
      3
      e– 2t
      2
Correct Option: A

Here Zeq =
1 .( 1 / Jω)
, ω = 1 on comparing with I (s) = u (t) cos
1 + (1 / Jω)


or Z eq =
1
1 + J

Since initial voltage on the capacitor is V(0) = 2 V,
so, V (t) J (s), Zeq = cos t.
1
+ A e– st
1 + J

s=
1
cos (t– 45°) + A e– st given that at t = 0. V (0) = 2 V
2

so, 2 =
1
2 cos (0 – 45º) + A e–5.0
2

2 =
1
2 + A
2

or A =
3
2

S =
1
=
1
= 1
RC1 x 1

V (t) = cos (t – 45°) +
3
e– t
2



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