1.

Solve the differential equation of L-C circuit and obtain the expression of current.

Answer»

Solution :The differential equation of L-C circuit is,
`(d^(2)Q)/( dt^(2))+(1)/(LC) q = 0`
The solution of the equation is,
`q= q_(m) COS ( omega_(0) t+ phi)`…(1)
where `q_(m)` is the maximum VALUE OFQ and `phi` is phase constant.
At t= 0, `q= q_(m)`
`:. q_(m) = q_(m) cos phi`
`:. 1 = cos phi`
`:. phi = 0^(@)`
`:.` From equation (1),
`q = q_(m) cos ( omega_(0) t)`
Differentiating w.r.t. time t,
`(DQ)/(dt) = q_(m) omega_(0)( - sin omega_(0)t)`
but `(dq)/(dt)= -1`
`:. -I = - q_(m) omega_(0) sin omega_(0) t `
`:. I = I_(m) sin omega_(0) t `
where,` q_(m) omega _(0) =I_(m) `
`:. I = I_(m) sin omega_(0) t`


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