Is a 40w Bulb Efficient at 120v?

In summary, the question is asking how many watts a 40 watt bulb should use at a voltage of 120 volts. This is the standard voltage in the U.S. and light bulbs will typically use the wattage as marked. In the UK, bulbs are rated at 240 volts, but the EU standard is 230 volts. Electrical supply into homes may vary, leading to differences in the measured power consumption. Overall, the question is seeking clarification on the power consumption of a 40 watt bulb at a specific voltage.
  • #1
kgal
43
0
How many watts should a 40w bulb use at 120v?
 
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  • #2
40 watts?

wikipedia has a discussion on watts and watt-hours that might clear up things.
 
  • #3
THe bulb would be marked as using 40W at a specified voltage. If you don't know that information, you can't answer the question.
 
  • #4
In the U.S. standard voltage is 120 volts, so light bulbs will use the wattage as marked.
 
  • #5
Due to what I believe is partly an historic anomaly, bulbs in the UK are rated at 240V, but 230V is the EU voltage standard which should be delivered to UK homes.

I think in part it is usual to rate the bulb at a higher voltage as the life expectancy [of filament bulbs] drops exponentially once above the rated voltage. So bulbs may be sold into a market with voltage ratings slightly in excess of the specified volts.

Electrical supply into homes is rarely that accurate, at least in UK. My own house suffered for years at variable under-voltage. We share a relatively small spur with an industrial estate. It dropped (I kid you not) to 183V on one occasion I was measuring it myself. I complained to the elec co and they did some work. I then had >250V for several months until I complained enough they installed £70,000 of new kit in the local sub-station.
 
  • #6
That's a power use figure, like one on a frig or work tool...it's not an indicator
of how much light it produces...
 
  • #7
Naty1 said:
That's a power use figure, like one on a frig or work tool...it's not an indicator
of how much light it produces...

Hence the question "How many watts should a 40w bulb use..."

:confused:
 
  • #8
cmb said:
Hence the question "How many watts should a 40w bulb use..."

:confused:
As previously stated, forty watts at the voltage specified by the manufacturer.

Due to a variety of factors, the measured power consumption will vary from the advertised value.
 
  • #9
pantaz said:
As previously stated, forty watts at the voltage specified by the manufacturer.

Due to a variety of factors, the measured power consumption will vary from the advertised value.

Yes, I know that, but Naty 1 didn't appear to get the question.
 

What is the power output of a 40w bulb when used at 120v?

The power output of a 40w bulb when used at 120v is 40 watts.

How does the voltage affect the power output of a 40w bulb?

The voltage directly affects the power output of a 40w bulb. When the voltage is increased, the power output also increases and vice versa.

What is the energy consumption of a 40w bulb when used at 120v?

The energy consumption of a 40w bulb when used at 120v is 40 watt-hours (Wh).

Can I use a 40w bulb at a higher voltage?

No, it is not recommended to use a 40w bulb at a higher voltage as it can cause the bulb to overheat and potentially lead to a fire hazard.

What is the lifespan of a 40w bulb when used at 120v?

The lifespan of a 40w bulb when used at 120v can vary depending on the specific bulb and usage, but on average it can last for about 1,000 hours.

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