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03-25-2008, 07:46 PM
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Master Journeyman
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Join Date: Jul 2004
Location: Saint Regis Falls, NY, USA.
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Question for Speedy-Petey
If you have a lamp rated 60 watts that normally operates on 240 volts, what would be the current draw if it operates on 120 volts?
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03-25-2008, 10:11 PM
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Master Handyman
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Join Date: Nov 2006
Location: Upstate, NY
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Whatever math I did was wrong.
This is the best I could come up with.
I'll stick to doing things how I know.
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No, that's not me in the avatar. I just like the picture. 
Last edited by Speedy Petey : 03-26-2008 at 06:11 AM.
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03-26-2008, 12:24 AM
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Master Journeyman
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Join Date: Apr 2004
Location: Sharon, PA, USA.
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Unless I am doing something wrong, I get .5A
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03-26-2008, 03:48 AM
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Master Journeyman
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Join Date: Jul 2004
Location: Saint Regis Falls, NY, USA.
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The POWER represented by P never changes. P=EI - The E or voltage is a variable and I the current is variable.
60 divided by 240 equals a quarter amp. 60 divided by 120 equals a half amp. Because you are operating the 240 bulb at half its rated voltage the amperage is double its normal operating amperage. Therefore the bulb operates at a half amp.
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03-26-2008, 06:10 AM
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Master Handyman
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Join Date: Nov 2006
Location: Upstate, NY
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SO then why did you ask?
Was this some sort of test?
I always knew a lamp worked at half wattage at half voltage, so I did the math to see if I my thinking was correct and came up different. I was wrong because I did the wrong math. I thought into it too much.
I should have stuck to my instinct.
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No, that's not me in the avatar. I just like the picture.
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03-26-2008, 06:15 AM
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Apprentice
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Join Date: Mar 2006
Location: North Carolina
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Just to make sure I have this straight, the 60 watt lamp at 240 volts glows at 60 watts (naturally), so at 120 volts it would glow at only 15 watts a 1/4 of it's rated output with 1/2 of the power supply ?
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03-26-2008, 07:35 AM
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Master Journeyman
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Join Date: Jul 2004
Location: Saint Regis Falls, NY, USA.
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No, no test. Just a problem for discussion. All the incandescent nightlights I have in my house are 240 volt 6S6 bulbs. I put these in - in the year 2000 and they are still working. The 6S6 bulb has a base like the old Xmas tree bulbs. The 60 watt bulb operating at 240 volts draws a quarter amp. If you operate it at 120 volts the wattage reduces by one-half. The current is the same a quarter amp. 60 divided by 240 = .25. 30 divided by 120 = .25.
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03-27-2008, 06:24 AM
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Master Handyman
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Join Date: Nov 2006
Location: Upstate, NY
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No Push.
60w@ 240v = 30w@120v
I over though it and confused myself over something extremely simple.
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No, that's not me in the avatar. I just like the picture.
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03-27-2008, 06:42 AM
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Master Journeyman
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Join Date: Jul 2004
Location: Saint Regis Falls, NY, USA.
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Alot of people do that. They don't think "out of the box" Don't you find many people complicating something simple? Engineers are good for that. Take a simple switch and add a bunch of relays - Boom! complicated circuits.
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03-27-2008, 06:59 PM
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Apprentice
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Join Date: Mar 2006
Location: North Carolina
Posts: 289
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Thanks speedy....Now I'm unconfused.
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