


Thread Tools  Display Modes 
06182008, 08:17 AM  #16 
Newbie
Join Date: Jun 2008
Posts: 2
Rewards Points: 10

Amp / Watt analysis
I was referring to the second question of the original post about the 1875 watt Hair dryer.
1875 / 110 would be about 17 amps but here is the trick: 1875 / 125 would give 15 amps. I'm sure that if you look closely at the Hair dryer you will see it is rated at 1875 watts at 125 volts. So its a B.S. marketing trick to have "more power" example: It features 1875 watts of maximum drying power, high/low heat settings and a cool shot button that locks style into place. A detachable styling nozzle is included. Hairdryer is full size with a UC standard ALCI safety plug. Power AC 125V/60HZ. Length of dryer is 8". AdvertisementLast edited by evmsmd09; 06182008 at 08:23 AM. 
06182008, 05:48 PM  #17  
Advice worth 2 cents!
Join Date: Mar 2008
Location: Quebec, Canada
Posts: 229
Rewards Points: 150

Amp / Watt analysisQuote:
 pete ps..You made a very good point, I'm just BSing...lol
__________________
pete 

09192011, 02:38 AM  #18  
Newbie
Join Date: Sep 2011
Posts: 6
Rewards Points: 10

Amp / Watt analysisQuote:
Ok here is my question. Amps = Watts divided by Volts now here in SA we use 220 volts. So if im using 1875 watts of power, its less amps than if it was 110, because unlike Ohms law, in this equation, higher volts drops the amps. 1875 watt / 220 volts = 8.52 amps 1875 watt / 110 volts = 17 amps 

09192011, 02:45 AM  #19  
Newbie
Join Date: Sep 2011
Posts: 6
Rewards Points: 10

Amp / Watt analysisQuote:
Ok so here is my question. HairDryer = 1875 watt Amps = Watts divided by volts We use 220volt here, so Amps = 1875 / 220 = 8.2 Or Amps = 1875 / 110 = 17 So unlike Ohms law, in this equation, more volts = less amps. I Still can't see how a hello kitty hair dryer is gonna such 15 amps. Then a stove on grill would take like 80 amps, more than a average house hold breaker. 

09192011, 05:53 AM  #20 
Member
Join Date: Oct 2010
Location: Cairns Australia
Posts: 3,074
Rewards Points: 3,108

Amp / Watt analysis
You still have much to learn !
A hair dryer can easily pull 1800w. Due mainly to the heating element. Most heating elements use a rather large amount of power. And a stove grilling element would easily pull a like wise amount of power. But 80a is not not just for the grill. That would be everything at once. oven , grill , and hot plates all together. In Australia 240v mains, stove circuits are usually 30 to 40a. Cause your half that voltage 120v, You would be double that amperage. So 60 to 80a would be about right. Keep reading and digesting ! Last edited by dmxtothemax; 09192011 at 06:10 AM. 
09192011, 06:10 AM  #21  
Newbie
Join Date: Sep 2011
Posts: 6
Rewards Points: 10

Amp / Watt analysisQuote:
Dont forget that even the greatest minds of electricity, pretty much all say that at best, we know nothing about current and electricity. To em there are alot of contradictions, some stuff seems to work most of the time, but in certain cases, it does not work out. Also if you couldn answer my question on why Ohms law increases Amps, where as amps = watts over volts decreases it. Now for pudding 

09192011, 06:56 AM  #22 
Electrician
Join Date: Aug 2008
Location: Near Jackson Michigan Area
Posts: 1,451
Rewards Points: 502

Amp / Watt analysis
Ohm’s Law: P=IE E=IR
Change them anyway using standard mathematics. P=IE is the same as I=P/E…plug in some numbers….E=240, P=1800, do the math and I=7.5 Now if E=120, P=1800, I=15. In the case of a 1800 watt hair dryer, the value of P (watts) is fixed. So if ‘P’ is fixed and ‘E’ is changed, that means ‘I’ will have to change in order for ‘P’ to still equal 1800. In the case of P=IE, I & E are inversely proportional. If one goes up, the other must go down in order for ‘P’ to be the same.
__________________
Kyle Just because you can, doesn't always mean you should 
09192011, 07:00 AM  #23  
Newbie
Join Date: Sep 2011
Posts: 6
Rewards Points: 10

Amp / Watt analysisQuote:
Then why is there a equation Apms = Watts / volts Im using 2000 Watts @ 220 volts Amps = 9 

09192011, 07:13 AM  #24 
Lic Elect/Inspector/CPO
Join Date: Apr 2011
Location: NJ
Posts: 369
Rewards Points: 250

Amp / Watt analysis
When changing from 110v to 220 v the ampergae will go down, actually in half.
This is why some motors are rated to be wired either way. It is be economical to run at higher voltage and lower amps. Ex. swimming pool motors. 
09192011, 07:35 AM  #25 
Electrician
Join Date: Aug 2008
Location: Near Jackson Michigan Area
Posts: 1,451
Rewards Points: 502

Amp / Watt analysis
Because P=IE, P=Watts, E=Voltage, I=Current (Amps). Divide both sides of the equation by E, and the equation becomes I=P/E. Divide both sides of P=IE, by I and it becomes E=P/I.
You divide 2000 watts by 240 volts, not 220V, as the system nominal voltage is 240V. Your answer is I=8.333~
__________________
Kyle Just because you can, doesn't always mean you should 
09192011, 09:01 AM  #26 
Member
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 7,168
Rewards Points: 2,436

Amp / Watt analysis
For everyday electrical purposes just use watts equals volts times amperes.
At all times, for heating elements, amperes equals volts divided by resistance (Ohm's Law). Ohm's law is also true for motors, inductive loads,and electronics where it is stated as amperes equals volts divided by impedance and the actual mathematics is somewhat more complicated (for you math whizzes, complex, no pun intended). For load calculations in the U.S., assume (and use in your calculations) 120 volts or 240 volts. The actual amperes drawn and watts consumed by heating appliances given a slightly different voltage (like 110 or 208) is not predictable because the temperature of the heating elements varies with the voltage and the resistance varies with the temperature. You do not compute amperes required by measuring the resistance of the heating element when it is cold and the power is off (power off is mandatory for resistance or continuity measurements)
__________________
(One morning on WRKO Radio) The tub's not clean! Let's remodel the bathroom. (One afternoon on WRKO Radio) It's time for an oil change. I'm going to trade in the car for next year's model. Last edited by AllanJ; 09192011 at 10:15 AM. 
09192011, 09:53 AM  #27  
JOATMON
Join Date: Aug 2011
Location: S. California
Posts: 8,285
Rewards Points: 3,844

Amp / Watt analysisQuote:
And....where was that "Hello Kitty" hair dryer made? China? I would be willing to bet that it is not pulling the full 1800W.....good chance the 'rating' is based on perfect conditions with maybe the supply voltage 'tweaked' a little to get the wattage up. By the time you add up the voltage drop due to your wiring and the cheap cord (which most likely has 16 gauge or smaller wire) they put on there....I doubt your doing more than about 1500w...
__________________
Even if you are on the right track, you will still get run over if you just sit there. My 2Story Addition Build in Progress Link ... My Garage Build Link and My Jeep Build Link 

The Following User Says Thank You to ddawg16 For This Useful Post: 
LivingLight (09202011)

09202011, 06:40 PM  #28  
Member
Join Date: Oct 2010
Location: Cairns Australia
Posts: 3,074
Rewards Points: 3,108

Amp / Watt analysisQuote:
The amount of power used is still the same. Voltage might change but power doesnt ! Cause as one changes the other also changes. SEE  SAW ! 

09212011, 01:43 AM  #29  
Newbie
Join Date: Sep 2011
Posts: 6
Rewards Points: 10

Amp / Watt analysisQuote:
Amps = Watts DIVIDED by VOLTS How can volts going up not change amps in a three way formula? Last edited by LivingLight; 09212011 at 01:46 AM. Reason: missing a "e" 

09212011, 06:31 AM  #30  
Electrical Contractor
Join Date: Jun 2004
Location: Newnan GA
Posts: 6,185
Rewards Points: 2,766

Amp / Watt analysisQuote:
100w/120v=.833amps 100w/240v=.416amps Watts is the measure of power. Advertisement
__________________
Yes I am a Pirate, 200 years too late. "Jimmy Buffett" 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Switching from incandescent to CFL  Mooe  Electrical  8  12252007 11:27 AM 
help me solve this mystery please  lindaberrien  Roofing/Siding  17  06122007 01:06 AM 
100 Watt Max  Big Bill  Electrical  2  03292007 05:34 PM 