ohms resistance
- Thread starter cardiy
- Start date
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Cardiy - wouldn't you be better off getting yourself onto some properly organised training rather than just asking random questions on a DIY site?
Ban this is a diy forum ,how do you know why i am asking the question ,if you dont like answering questions you dont have to,why are you such a negative person .There are so very helpful people who take time to answer peoples questions ,sadly you seemed not to be one of them .
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I don't know why you're asking, but following the what you're asking paints a picture of someone trying to learn a subject, not a DIYer asking how to do a particular job.
Nothing whatsoever wrong with trying to learn, but it's precisely because I'm not negative that I said what I did - asking random questions here like How do you work out what the ohms resistance should be on appliances kettle, electric fire ,hairdryer and motors etc and Hi can any one explain what is 3 phase thanks,how it works is not an efficient way to go about it.
You proved that yourself:
On the 18th of March you asked this:
That's actually all one subject, 2 inter-related topics, but you are going about things in a very haphazard way.
Nothing whatsoever wrong with trying to learn, but it's precisely because I'm not negative that I said what I did - asking random questions here like How do you work out what the ohms resistance should be on appliances kettle, electric fire ,hairdryer and motors etc and Hi can any one explain what is 3 phase thanks,how it works is not an efficient way to go about it.
You proved that yourself:
On the 18th of March you asked this:
And then 3 days later you were back with this:
That's actually all one subject, 2 inter-related topics, but you are going about things in a very haphazard way.
Bas ,i am a diyer but some of the topics i have posted i had seen on other forums but were not fully explained unlike this site , i only asked some of the topics out of interest,dont worry i am not doing any illegal electric works.
there's no such thing as illegal electrics.. it's not against the law for you to do any electrical worn in your own home ( with the exception of the DNO's equipment, the meters and main fuse etc... ), but some of it is notifiable so that it gets checked by someone that you are doing it right..
without getting into the inductive reactance side of things, ohms law is pretty simple..
Voltage = Current x Resistance
and
Wattage = Voltage x Current..
so..
Wattage = (Current x Resistance) x Current
or
Wattage = Current² x Resistance
also
Wattage = Voltage x (Voltage / Resistance )
or
Wattage = Voltage²/Resistance
so
Resistance = Voltage²/Wattage ( is that right? I've confused myself.. )
so a 3000W kettle for example would be
R = 230X230
3000
R = 17.633333 ohms....
but in reality somewhere around that is ok..
without getting into the inductive reactance side of things, ohms law is pretty simple..
Voltage = Current x Resistance
and
Wattage = Voltage x Current..
so..
Wattage = (Current x Resistance) x Current
or
Wattage = Current² x Resistance
also
Wattage = Voltage x (Voltage / Resistance )
or
Wattage = Voltage²/Resistance
so
Resistance = Voltage²/Wattage ( is that right? I've confused myself.. )
so a 3000W kettle for example would be
R = 230X230
3000
R = 17.633333 ohms....
but in reality somewhere around that is ok..
No, (230 x 230)/16, not 0.16.
Surely you don't need advice on how to operate a calculator?
This also all begs the question: why exactly would you want/need to know the resistances of your home appliances?
As above, the nice simple linear relationship between power, voltage and resistance can only be applied directly to a small selection of devices that present a purely resistive load. In general, only heating devices are purely resistive.
Ordinary tungsten filament lamps are heating devices - ones that get so hot they glow in the dark!
Any device containing an inductive or capacitive load, that includes anything containing a motor, a transformer or a switched mode power supply, cannot be described by a two dimensional relationship you can easily plot on a piece of graph paper. The maths starts getting more complicated, involving complex numbers (usually reprsented by 'i' or 'j'). Both are considered as at right angles to reality (and at right angles to each other)
The upshot of all that is testing most AC powered domestic devices with a DC multimeter will probably produce inconsistent results.
Ordinary tungsten filament lamps are heating devices - ones that get so hot they glow in the dark!
Any device containing an inductive or capacitive load, that includes anything containing a motor, a transformer or a switched mode power supply, cannot be described by a two dimensional relationship you can easily plot on a piece of graph paper. The maths starts getting more complicated, involving complex numbers (usually reprsented by 'i' or 'j'). Both are considered as at right angles to reality (and at right angles to each other)
The upshot of all that is testing most AC powered domestic devices with a DC multimeter will probably produce inconsistent results.
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