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 Dimmer Efficiency
Name: Jonathan N.
Status: Other
Age: 40s
Location: N/A
Country: N/A
Date: June 2003


Question:
Somebody told me that common light dimmers use as much electrical energy if they are turned up to 100% as they do when they are turned down... to 25% (for instance). Is this true? I do not know too much about electricity, but it seemed to me that it would be more like a water faucet...



Replies:
They do not use as much energy when turned down. You would know if they did, because the energy that did not go to the light would have to go somewhere, and you could hardly fail to notice it. The dimmer would get hot, for example.

Common light dimmers are more like a pulsating shower head than a faucet. They allow current though for a fraction of each cycle (of 60 Hz), and then they stop the current for the remainder of the cycle.

Tim Mooney


"Old time" dimmer switches were just series resistors that dropped the voltage across a light bulb, but technology has long since replaced these relics. Dimmer switches are really pretty sophisticated now, and a detailed discussion here would not do the topic justice. Better that you look at the interesting web site "How Things Work" for the answer to this and many other "How Things Work" topics:

http://home.howstuffworks.com/dimmer-switch.htm/printable

Vince Calder



Click here to return to the Engineering 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