A Zener of power rating 1 W is to be used as a voltage regulator. If Zener has a breakdown of 5V and it has to regulate voltage which fluctuated between 3 V and 7 V, what should be the value of `R_(s)` for safe operation (see figure) ?

Explanation

Given `p=1 W`
`V_(E) = 3 V ` to ` 7V`
Also `R_(g) (I_(z))_(max) = V_(8) - V_(z)`
`R_(8) = (V_(s) - V_(z))/( (I_(z))_(max)) = (2)/( 0.2) =10 Sigma`