A `100 W` bulb is designed to operate on a potential difference of `230 V`.
(i) Find the resistance of the bulb.
(ii) Find the current drawn by the bulb if it is operated at a potential difference for which it is designed.
(iii) Find the current drawn and power consumed by the bulb if it is connected to a `200 V` supply.

Explanation

Power rating of the bulb is `P_(0) = 100 W` , voltage and rating of the bulb is `V_(0) = 230 V`.
(i) Resistance of the bulb is
`R = ( V_(0)^(2))/( P_(0)) = ((230^(2)))/(100) = 529 omega`
Current drawn is
` I = (V_(0))/(R ) = ( 230) /( 529) = ( 10)/(23) A`
(iii) `I = (200)/(529) A rArr P = I^(2)R = ((200)/(529))^(2) xx 529 = 75.6 W`