An electric bulb rated '220 V, 60 W' glows when connected with 220 V mains.
Another identical bulb is connected in series with the first one and the system is connected across the 220 V mains. Draw a diagram to show the arrangement and find : (a) the rate of consumption of energy in each bulb, and (ii) total power consumed.

Explanation

Given : rating of bulb is 220 V, 60 W i.e., voltage V = 220 volt and power P = 60 watt.
The arrangement of two identical bulbs in series with the mains is shown in Fig. In this

arrangement voltage across each bulb will be
V = 110 volt.
(a) Rate of consumption of energy in each bulb
` = (V^2)/(R ) = ((110)^2)/(806.67 ) = 15 W`
Here we had assumed that the resistance of bulb does not change on glowing.
(b) Total power consumed in the two bulbs
`= 15 W + 15 W = 30 W`