Department of Energy Argonne National Laboratory Office of Science NEWTON's Homepage NEWTON's Homepage
NEWTON, Ask A Scientist!
NEWTON Home Page NEWTON Teachers Visit Our Archives Ask A Question How To Ask A Question Question of the Week Our Expert Scientists Volunteer at NEWTON! Frequently Asked Questions Referencing NEWTON About NEWTON About Ask A Scientist Education At Argonne Light Bulb Output Differences 
Name: N/A
Status: N/A
Age: N/A
Location: N/A
Country: N/A
Date: 1991
Question:
Different designs for light bulbs: How is one light bulb created to be powered by a 6 volt battery while another light bulb can be designed to operated from 120 V ac? When you talk about light bulbs, do they respond differently to AC and Dc? If I say I have a 6V source of light, if I use 120V, will the filament melt?


Replies:
A light bulb filament glows because it is hot. The filament is hot because electrical power is heating it. The power is I- squared R. Can you now answer your own questions? By the way, one can vary R by varying the length and thickness of the filament. Have I left out anything that you need to answer your question?

The above answer will get you started. However, there are more variables in this problem than there are constants. For example, the material the filament is made of can greatly vary its resistance with the amount of heat (watts) that it dissipates. In addition, sealed bulbs generally are in a semi-vacuum that has some ionized gases in the area around it to help the filament to glow. That is why GE and Phillips gets big bucks for the designs of very efficient light bulbs. Years of materials research have gone on in the design of bulbs, and in recent years they have become considerably more efficient.


Click here to return to the Physics Archives

NEWTON is an electronic community for Science, Math, and Computer Science K-12 Educators, sponsored and operated by Argonne National Laboratory's Educational Programs, Andrew Skipor, Ph.D., Head of Educational Programs.

For assistance with NEWTON contact a System Operator (help@newton.dep.anl.gov), or at Argonne's Educational Programs

NEWTON AND ASK A SCIENTIST
Educational Programs
Building 360
9700 S. Cass Ave.
Argonne, Illinois
60439-4845, USA
Update: June 2012
Weclome To Newton

Argonne National Laboratory