# Enery phisic question

hi here is the question

A 60 watt light bulb is left swithed on for 10 hours. If the light bulb is 15% effcient, calculate the amount of light energy produced in that time. what is the total energy consumption of the light bulb in this time.

so i need to find work done right so is that power divided by time to get the energy and then find 15% of that am i right i am bathed by this.

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Kurdt
Staff Emeritus
Gold Member
A watt is 1 unit of energy per unit time. You know how much of the energy was turned into light (15%) and the length of time the light was left on. No need to introduce work.

so do i divide watts by time taken?

so 60 watts divided by10 hours which is 6 15% of 6 is 0.9 if i am correct

can you please tell me if i am right if not can you advive me where i went wrong

Kurdt
Staff Emeritus
Gold Member
watts is per second whereas you're given a time in hours. Secondly do you think the energy would be lower or higher than how much you are using in one second?

so 10 hours is 600 minutes 36000 seconds and 60 watts goes goes in in 36000 2160000 so 15% 324000 am i right

Kurdt
Staff Emeritus