Yes John is right see below.
If I can now explain a bit more for those who may want to know why VA is not always equal to watts in some situations, it is all to do with resonance (reactance) really means how everything around us has so called natural resonance, if you strike a glass thimble, it will produce a decaying high frequency in kilo herts sound waves, same way if you strike a big base drum, it will produce very low frequency under 100 herts, so when we instead of striking it with our stick, we use a voltage stick to strike, we have to then strike it such that it will use minimum power to continue to produce that sound wave, so our voltage stick must be matched to the resonant frequency of the object, for example if the drum was vibrating up and down, and if we struck it to go down whilst it was coming up, we would be opposing it more, so we would need more energy to make it continue to produce sound wave, but if the drum's skin was already going down naturally then we would only need a gentle strike to it to continue to produce constant sound pressure wave, another example would be a swing, you would push the swing when it is swinging away, but if you pushed it whilst it was still swinging towards you, you would not only disturb its swing but also spend a lot of energy to swing it in opposite direction.
So most ac electrical circuits using inductive components (Like electrical motors or transformers with coil winding in conjunction with their parasitic capacitance) have so called nature resonant frequency, but our mains power is fed at 50hz, so this does not necessarily mean the voltage peaks of our mains will be happy to supply the load in exact sympathy with the natural resonant frequency of the load, so this then boils down to power factor, and it can be corrected using capacitors to change the resonant frequency of the inductive load such that net power comes down, and it is often referred to as matching load impedance with the source.
But yes in practice we need not worry too much about such issues as most inductive loads are matched to mains frequency at manufacture level, thus when you buy an electrical appliance which says 230v 50Hz, it means it has been designed to operate on that frequency, it may draw more current if the supply frequency changed to say 60 Herts.
so for most practical purposes we need not bother with power factors particularly on our single phase domestic appliances, it only becomes more relevant at high powered industrial appliances, so sleep well, I was just merely trying to explain what a power factor means in terms of matching an inductive load to an ac power source of fixed frequency.
There is a whole load of formulas and sine waves and angles and what not involved and I don't feel very comfortable going there as I never had any need to.
So for our daily lives, using everyday devises and for most appliances running within their designed power levels, we can deduce VA as equal to watts, of course if you were drilling a half inch hole in a thick metal sheet using a 400watt Black & Decker, at some stage it is going to come stuck and start drawing well over 1000 watts and overheat, because a stalled motor or a motor that is under heavy load is not running at a designed comfortable speed so its resonant frequency changes , it starts to produce less of so called back EMF and so start using far more current as it tries to catch up to its designed speed, so it will need to draw more power.
( i must add that in my example of a swing, is just an example and perhaps totally opposite to what goes in electrical inductive loads, here incoming voltage is opposed by so called back EMF voltage generated by all inductive loads, so for example a motor free running, let us say at 2000 rpm, with no load, generates say 200V and incoming volts applied to it is is 230 but of opposite polarity, here the net result is (+230)- (-200 )= 30v so out motor is drawing power equal to a 30v net supply and since its windings resistance does not change, and let us say it is 10 ohms, so it draws 30/10 = 3amps, our motor is using 30v x 3amps = 90watts, but now say it is subjected to a load, and its speed drops to 1500 rpm, so now its back EMF also falls so instead of producing 200v it is now producing say 170V, so now the power being used by that motor is (+230)- (-170) = 60v and since its windings resistance has not changed and is still 10 ohms, so now it will start drawing 60/10 = 6amps , so it will now be using 60 x 6 = 360watts !)
If I can now explain a bit more for those who may want to know why VA is not always equal to watts in some situations, it is all to do with resonance (reactance) really means how everything around us has so called natural resonance, if you strike a glass thimble, it will produce a decaying high frequency in kilo herts sound waves, same way if you strike a big base drum, it will produce very low frequency under 100 herts, so when we instead of striking it with our stick, we use a voltage stick to strike, we have to then strike it such that it will use minimum power to continue to produce that sound wave, so our voltage stick must be matched to the resonant frequency of the object, for example if the drum was vibrating up and down, and if we struck it to go down whilst it was coming up, we would be opposing it more, so we would need more energy to make it continue to produce sound wave, but if the drum's skin was already going down naturally then we would only need a gentle strike to it to continue to produce constant sound pressure wave, another example would be a swing, you would push the swing when it is swinging away, but if you pushed it whilst it was still swinging towards you, you would not only disturb its swing but also spend a lot of energy to swing it in opposite direction.
So most ac electrical circuits using inductive components (Like electrical motors or transformers with coil winding in conjunction with their parasitic capacitance) have so called nature resonant frequency, but our mains power is fed at 50hz, so this does not necessarily mean the voltage peaks of our mains will be happy to supply the load in exact sympathy with the natural resonant frequency of the load, so this then boils down to power factor, and it can be corrected using capacitors to change the resonant frequency of the inductive load such that net power comes down, and it is often referred to as matching load impedance with the source.
But yes in practice we need not worry too much about such issues as most inductive loads are matched to mains frequency at manufacture level, thus when you buy an electrical appliance which says 230v 50Hz, it means it has been designed to operate on that frequency, it may draw more current if the supply frequency changed to say 60 Herts.
so for most practical purposes we need not bother with power factors particularly on our single phase domestic appliances, it only becomes more relevant at high powered industrial appliances, so sleep well, I was just merely trying to explain what a power factor means in terms of matching an inductive load to an ac power source of fixed frequency.
There is a whole load of formulas and sine waves and angles and what not involved and I don't feel very comfortable going there as I never had any need to.
So for our daily lives, using everyday devises and for most appliances running within their designed power levels, we can deduce VA as equal to watts, of course if you were drilling a half inch hole in a thick metal sheet using a 400watt Black & Decker, at some stage it is going to come stuck and start drawing well over 1000 watts and overheat, because a stalled motor or a motor that is under heavy load is not running at a designed comfortable speed so its resonant frequency changes , it starts to produce less of so called back EMF and so start using far more current as it tries to catch up to its designed speed, so it will need to draw more power.
( i must add that in my example of a swing, is just an example and perhaps totally opposite to what goes in electrical inductive loads, here incoming voltage is opposed by so called back EMF voltage generated by all inductive loads, so for example a motor free running, let us say at 2000 rpm, with no load, generates say 200V and incoming volts applied to it is is 230 but of opposite polarity, here the net result is (+230)- (-200 )= 30v so out motor is drawing power equal to a 30v net supply and since its windings resistance does not change, and let us say it is 10 ohms, so it draws 30/10 = 3amps, our motor is using 30v x 3amps = 90watts, but now say it is subjected to a load, and its speed drops to 1500 rpm, so now its back EMF also falls so instead of producing 200v it is now producing say 170V, so now the power being used by that motor is (+230)- (-170) = 60v and since its windings resistance has not changed and is still 10 ohms, so now it will start drawing 60/10 = 6amps , so it will now be using 60 x 6 = 360watts !)
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