[DMCForum] Re: Last Post For Martin
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[DMCForum] Re: Last Post For Martin



Hi Martin.

>I can't remember how to get
> power as it relates to force in a strait line - can you help?

Force:  Newtons, nevermind the definition

Work: straight line Force*distance.  Joule


If it takes 500N to push your Delorean, and you push it 3m,
you've done 1500J of work.  Doesn't matter how fast you're going.

Power: work/time (Joule/second), or force*speed (Newton*(m/s))  Watt

If your Delorean in the above push is going 1.5m/s, you're expending
750 Watts of power

> As an electronics wizz, you'll know this one then - when is it not
> proper to express electric power transfer in Watts, but rather in
> VoltAmps? I can't remember (!)

If you have a component that has a lot of capacitance or inductance,
and you put alternating current through it, the peaks in current and
voltage don't line up, they become out of phase, and they don't
multiply right.
For instance, you could have a component that has 1Volt across it,
and 1Ampere going through it, and it would not be putting out 1Watt
in heat, like you'd expect; it would be putting out less.  Since
1Watt=1Watt=1Watt, one is not allowed to multiply this 1Volt and 1Amp
together to produce 1Watt.
It is appropriate, in this case to say the component is using 1
VoltAmp.  VoltAmp is a word used by convention to denote ac voltage*
ac current that isn't necessarily in phase. 


Rick.






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