# Homework Help: Heat energy out of 500 w halogen bulb?

1. Aug 29, 2008

### vishnukorde

heat energy out of 500 w halogen bulb???

how much heat energy is liberated out of a 500W halogen bulb??>????
what temp is reached in 1 min.

2. Aug 29, 2008

### chroot

Staff Emeritus
Re: heat energy out of 500 w halogen bulb???

It's impossible to say without more information. The bulb produces 500W of both heat and light combined, but the specifics of the bulb's construction determines how much of each.

- Warren

3. Aug 29, 2008

### Topher925

Re: heat energy out of 500 w halogen bulb???

If I had to guess Id say about 450 Watts. The temp I'm guessing is around 60C in one minute.

4. Aug 29, 2008

### LowlyPion

Re: heat energy out of 500 w halogen bulb???

How would you treat light that gets absorbed? If you treat all light as getting absorbed within a room with no windows isn't all the power going into heat - eventually?

5. Aug 29, 2008

### Topher925

Re: heat energy out of 500 w halogen bulb???

Isn't that what happens with all light?

6. Aug 29, 2008

### LowlyPion

Re: heat energy out of 500 w halogen bulb???

I said "eventually" because until the light is absorbed somewhere mustn't you presume that it is light in transit until absorbed, even if the eventually part of it may be a very small period of time for a small room?

7. Aug 29, 2008

### chroot

Staff Emeritus
Re: heat energy out of 500 w halogen bulb???

Yes, that's true, but the OP never mentioned anything about light-tight rooms, etc.

- Warren

8. Aug 29, 2008

### LowlyPion

Re: heat energy out of 500 w halogen bulb???

Not to carry the point too far afield, and keeping in mind the introductory nature of such a question as the OP, doesn't it depend on how you go about measuring for heat v. power?

If you fail to account for the measurement of all the heat generated, regardless of the room, doesn't that mean that you have measured inaccurately and not that the heat is only just what you measured and failed to capture from the light that escapes?

The temperature reached after 1 minute to me is the more indeterminate idea.

9. Aug 29, 2008

### chroot

Staff Emeritus
Re: heat energy out of 500 w halogen bulb???

Why are we beating this dead horse? There's not enough information to answer the question, so the thread's done. I'm not really interested in debating the engineering of a proper calorimeter. Suffice to say that yes, if you want a good measurement, you should probably build a good measurement apparatus.

- Warren

10. Aug 29, 2008

### Staff: Mentor

Re: heat energy out of 500 w halogen bulb???

If what the OP is asking in the first question is the efficiency (watts of light vs total watts) of the bulb, that can be found easily enough with a google: http://en.wikipedia.org/wiki/Incandescent_light_bulb#Luminous_efficacy_and_efficiency

There are actually two types, with efficiencies of 2.3 and 3.5%.

The operating temperature is reached in just a few seconds and it can also be found via google: http://hypertextbook.com/facts/2003/ElaineDevora.shtml

It's somewhere between 3000 and 3400K.

As others have pointed out, in most real-world situations very, very little of the light does not become heat so for practical calculations (for example, when determining an air conditioning load) you can probably simplly assume all of it becomes heat.