Question

An electric bulb of 100 W is used for 4 hrs a
day. Calculate the energy consumed by it in a day in Joules and kilowatt hour unit.

Answer 1

we know,
power=work done /time
also,
power = energy consumed /time
therefore , in one day ,energy consumed =power *time
=100*4*60 [since time is in hrs we will convert to seconds]
= 24000 J
therefore energy consumed in 15 days =24000*15 J
= 360000 J

Answer 2

Question :

An electric bulb of 100 W is used for 4 hrs a day. Calculate the energy consumed by it in a day in Joules and kilowatt hour unit.

Answer :

Power rating of the bulb:  100 W

Duration used each day:   4 hr

Number of days:               15

Total energy consumed by the electric bulb:  

   = power * duration

    = 100 W * 4 hrs/day * 15 days

    = 6000 W-hrs

  = 6 kWh

So energy consumed is  6 units.