Question #4dd1e

1 Answer
P dilip_k
Oct 22, 2016

#20W#

Explanation:

Let the resistance of each 60W bulb be #ROmega#
When connected in series the combination will have equivalent resistance #=3ROmega#

Power of each lamp #P=60W#

If supply voltage be #E " Volt"# then #"Power"(P)=E^2/R#
#=>60=E^2/R#

When the combination is connected to the mains, then total power consumed by the combination will be

#P_"comb"=E^2/(3R)=1/3xx60W=20W#

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