Derive an expression of affective resistance of four resistors connected in parallel.

Explanation

A current I enterining the combination gets dvided into `I _(1), I _(2), I _(3) and I_(4)` through `R_(1), R_(2), R_(3) and R_(4)` respectively.
such that `I=I_(1) + I_(2) + I_(3) +I_(4)`
By Ohm.s law
`I_(1)= (V)/(R_(1)), I _(2) = (V)/(R_(2)), I _(3) = (V)/(R_(3)) , I _(4) = (V)/(R_(4)) and I = (v)/(R_(P))`
where `R_(P)` is the equivalent of effective resistance of the paralel conbination.
`therefore (V)/( R _(P)) = (V)/( R _(2)) + (V)/( R _(2)) + (V)/( R _(3)) + (V)/( R _(4))`
`(1)/( R _(P)) =(1)/( R _(1)) + (1)/( R _(2)) + (1)/( R _(3)) + ( 1 )/( R _(4))`