Two incandescent lamps (25 W , 120 V ) and (100W , 120 V ) are connnected in series across a 240 V supply . Assuming that the resistances of the lamps do not vary with current ,find the power dissipated in each lamp after the connection .

Explanation

The resistance of the lamp 25 W - 120V ,
`R_(1)=(120)^(2)/(25)=576Omega`
The resiatance of the lamp 100 W - 120 V , `R_(2)=(120)^(2)/(100)=144Omega`
When the lamp is connected in series , the equivalent resistance of the circuit ,
`R'=576+144=720Omega`
`therefore` Current flowing through the circuit `(240)/(720)=0.33A`
`therefore` Power dissipated in the e first bulb `=(0.33)^(2)xx144=62.72W`
`therefore` power dissipated in the second bulb = `(0.33)^(2)xx144=15.68W`