Question

bulb of rating 60 watt 220 volt 250 watt and 220 volt are connected in series and their combination is connected to 440 volt supply but which bulb will fuse​

Answer 1

Answer : 60w

Explanation :

Resistance through 60 w bulb R = V^2/P = 220*220/60 = 806.66 Ohm

Same way Resistance through 250w bulb = 220*220/250=193.6 Ohm

Both bulb are connected in series with 440V supply

so current in that arrangement

I = V/R = 440/(806.66+193.6) = 0.44 Amps (Approx)

In this arrangement the P.D. across 60W bulb V = IR = 0.44*806.66 = 354.83 volt

P.D. across 250W Bulb = 0.44*193.6 = 85.18 volt

So 60W bulb will fuse because it can not tolerate 354.83 Volt (much more than 220 Volt)

Explanation: