When a light bulb is rated at 120Watts. Is that how much it uses per minute? Per hour? What specificly is this meaning?
2007-06-01 14:05:37 · 4 answers · asked by ookami_douketsu 1 in Science & Mathematics ➔ Engineering
When turned on, the bulb is consuming 120 watts continuously.
Your electric company probably charges you in kilowatt-hours. (kWh)
120 watts = .12 kilowatts.
If the bulb is left on for five hours, you would use:
.12 kilowatts x 5 hours = .60 kWh.
If it is used for five hours every day of the month, the contribution to your monthly electric bill would be:
.60 kWh per day x 30 days = 18 kWh
2007-06-01 14:15:21 · answer #1 · answered by Thomas C 6 · 1⤊ 0⤋
It mean the bulb consume 120Watts continuously as it being switched on.
The utility company will charge according to the total of Watts multiply with the length of time.
Watt (kW) x hour = kWh.
2007-06-01 21:50:02 · answer #2 · answered by new_once 5 · 0⤊ 0⤋
Watts are a measure of the amount of energy flowing through the wires and the bulb per second. Technically, this is a measure of power. Electric energy is consumed by light bulbs and other electric devices and converted to other forms of energy, like heat, light and mechanical energy for moving things around. Energy can be measured in joules, pound-feet, BTU's, calories and other measures.
120 watts of electric power can be converted to 120 joule/second or 89 pound-feet/sec of power by an electric motor, or 0.11 BTU/sec. of heat by an electric heater. An incandescent light bulb is basically an electric heater that produces a little visible light as a byproduct.
Electricity consumption is usually measured in watt-seconds or kilowatt hours. If you use 1 watt of power for 1 second you have used 1 watt-second of energy. 1000 watts running through the wires for an hour is 1 kilowatt hour.
A 120 watt bulb running for 8.3 hours would consume 1 kilowatt-hour of energy. Its output would be about .11 BTU/sec, which adds up in an hour to 410 BTU of heat with a little light on the side.
2007-06-01 22:34:53 · answer #3 · answered by mr.perfesser 5 · 0⤊ 1⤋
It means the light bulb delivers energy of 120 Joules per second.
2007-06-01 21:08:34 · answer #4 · answered by Tony H 2 · 0⤊ 0⤋