Heating effects of different lightbulbs

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SUMMARY

The discussion centers on the heating effects of LED and halogen light bulbs with identical power ratings. Both bulbs, despite having the same power input, exhibit different radiation spectra, with LEDs emitting significantly less infrared (IR) radiation compared to halogens. Participants agree that while both bulbs will eventually reach thermal equilibrium, the time taken to reach this state may differ due to the halogen bulb's higher heat output. The consensus is that the halogen bulb will likely maintain a higher temperature for a longer duration due to its greater heat dissipation through conduction and convection.

PREREQUISITES
  • Understanding of thermal equilibrium concepts
  • Knowledge of light bulb types: LED and halogen
  • Familiarity with power ratings and energy conservation principles
  • Basic principles of heat transfer: conduction, convection, and radiation
NEXT STEPS
  • Research the thermal properties of LED versus halogen bulbs
  • Explore the impact of different light bulb technologies on energy efficiency
  • Study the principles of heat transfer in enclosed systems
  • Investigate the lifespan and failure modes of LED and halogen bulbs under prolonged use
USEFUL FOR

This discussion is beneficial for electrical engineers, lighting designers, and anyone interested in the thermal performance and energy efficiency of different lighting technologies.

f todd baker
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Suppose I have two light bulbs, an LED and a halogen, but both have the same power P. Their radiation spectra are different, the LED radiating much less IR. Putting them in identical closets from which no heat may escape, will the walls and air in each come to some temperature T which, although increasing, will be the same for both?
 
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f todd baker said:
Suppose I have two light bulbs, an LED and a halogen, but both have the same power P. Their radiation spectra are different, the LED radiating much less IR. Putting them in identical closets from which no heat may escape, will the walls and air in each come to some temperature T which, although increasing, will be the same for both?

What do you think?

First can I check what you mean by "power P" ?

Is it..

a) The same power going into each light?
b) The same amount of visible light emitted by each light?
 
both consume and radiate the same power
what do I think? I think that there would be a time when both were at the same temperature ("equilibrium" between walls and air) and that temperature would be increasing. I think it possible that one would reach that equilibrium more quickly than the other.
 
f todd baker said:
both consume and radiate the same power

That can't be true (in the visible, the question you were asked) given your previous statement.

f todd baker said:
Their radiation spectra are different, the LED radiating much less IR.
 
I do not understand that. A bulb which is rated at 13 W, e.g. means that perhaps 8 W is radiated as visible light, 5 W as heat (IR). Whatever, whatever the bulb consumes must equal the energy radiated or else energy will be being stored somehow in the bulb.
 
F Todd: You are correct. Conservation of energy means all bulbs consume as much as they emit overall. That's why in b) I asked if you meant equal _visible_ output. (A 500 lumen halogen consumes more power than a 500 Lumen LED).

If the input power is the same then I would expect both boxes to behave more or less identically. However there might be minor differences. For example a halogen will be hotter than an LED so more of the power will leave the bulb by conduction/convection rather than radiation - so the temperature gradient between bulb and outside will be different (I think).
 
Last edited:
Sadly, the experiment will not run for very long as the LED lamp will overheat and fail long before the halogen lamp maxes out...
 

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