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Light bulb wattage

  • Thread starter marshall4
  • Start date
  • #1
50
0
How may watts does a 60-watt light bulb use in three hours?

60*3=180watts???
 

Answers and Replies

  • #2
Njorl
Science Advisor
258
10
Watts are a measure of power. Power is a rate of energy usage. "How many watts used in an hour?", is a nonsensical question.

Sensible questions would be:

-How many kilowatt-hours does a 60 watt bulb use in 3 hours?

-How many joules does a 60 watt bulb use in 3 hours?

Keeping in mind that a watt is 1 joule per second.


Njorl
 
  • #3
50
0
How many kilowatt-hours does a 60 watt bulb use in 3 hours?

how can i convert that to amps?
 
  • #4
Njorl
Science Advisor
258
10
Originally posted by marshall4
How many kilowatt-hours does a 60 watt bulb use in 3 hours?

how can i convert that to amps?
0.18

You can't.
 
  • #5
chroot
Staff Emeritus
Science Advisor
Gold Member
10,226
34
60 watts for 3 hours is 60 * 3 = 180 watt-hours. That's the same as 0.180 kilowatt-hours.

Your next question, "how do I convert that [kilowatt-hours] into amps?" is as non-sensical as the first question.

- Warren
 
  • #6
FZ+
1,561
2
how can i convert that to amps?
Amps = unit of current = rate of change of charge.

Volts = unit of electric potential

Joules = unit of energy.

Watt = unit of power = rate of change of energy

Kilowatt-Hours = Non-SI unit of energy

You cannot calculate current from power unless you know the voltage, or the resistance.
 
  • #7
50
0
ya, i'm confused
 
  • #8
ShawnD
Science Advisor
668
1
Watts and amps are both rates. They both stay constant and do not change with time.

To find the amps, divide by the watts by 120.
 
  • #9
FZ+
1,561
2
They both stay constant and do not change with time.
Uh... hmm. This is true (as a simplification) in this case, but is not always true.

To find the amps, divide by the watts by 120.
Not neccessarily. Depends on the country.
 

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