Re: Ohms Law

From: Dingus (dingus_at_iniindabababa.co.zu)
Date: 11/19/04 

Date: Fri, 19 Nov 2004 13:37:33 +1300

.. only one problem with this whole explanation.
There isn't any such thing as Ohmd Law - its all in the mind.

"jsmith" <juddo@ix.netcom.com> wrote in message
news:1100740099.jcC1kM/P7MMfqQsn8p+kiA@sonicnews...
>
>
> THE ESSENCE OF OHMS LAW
>
> by Jud Williams, Performance Power Technologies
>
> A lot of folks do not have a feeling of what the difference
> is between voltage and current or, for that matter, resistance. And
> then there is the
> term "power". Let's look at these terms and work toward a sense of
> feeling about them.
>
> Voltage is the hardest of the terms to understand because we have
> developed
> misconceptions due to hearing the term misused so often. Voltage is
> merely stored
> energy and really does not do anything useful. About all we can do
> with voltage is
> measure it. The thing that does all the work is current.
>
> Current is well named because it describes what it really does. Look
> at the current in a
> river. It is basically the same concept. As current flows, it is
> capable of doing work like
> floating some object down the river or turning a water wheel.
>
> Now, voltage does not do that. It just sits there as a potential.
For
> instance, the water
> held back by a dam is just like the voltage in a battery. The
voltage
> in the battery is not
> doing anything until something is hooked to the terminals which will
> allow current to flow.
> Then it is the current that does the work.
>
> That's simple, isn't it?
>
> As for power, it relates to how much work the current is doing. Take
a
> light bulb, for
> instance. They are always rated in Wattage and we know that they get
> very hot. That
> heat is caused by the current flowing through the filament. The
power
> is then related to
> the amount of heat that is generated. The hotter an object gets is
> generally related to
> the amount of power consumed.
>
> So now we can presume that if a device were to have current passing
> through it, it
> would become warm to some degree, if not hot. If we were to increase
> the amount of
> current through a device, it would become hotter. How would we cause
> the current to
> increase through the device in question? Well, let's say that we are
> using one battery to
> begin with and then add a second battery which would double the
> voltage. This
> additional battery causes an increase of current through the device
we
> are working
> with. Let's see how this happens.
>
> And now, we will get a bit technical. This will explain Ohms law and
> clear up some
> mysteries surrounding it. Take a resistor of some value such as 10
> Ohms. Note that we
> capitalize the word Ohm. That's because it is a person's name. But
to
> go on with the
> story, let's apply 12 volts across the resistor. Knowing these two
> values we can now
> calculate the amount of current that would be flowing through the
> resistor. Ohms law
> states that current (Amperes) is equal to the voltage, divided by
the
> value of the
> resistor. Divide 12 Volts by 10 Ohms and we get 1.2 Amperes.
Remember,
> we
> suggested that if we were to increase the voltage by adding another
> battery, additional
> current would flow. So let's add another 12 Volts and see what
> happens. 24 Volts
> divided by 10 ohms gives us 2.4 Amperes of current, just twice as
much
> as before. Do
> you think the resistor will get warmer as a result of this?
>
> Remember that the heat is a result of the power consumed by the
> resistor. Ohms law
> for power is current multiplied by Voltage. P equals I x E or "pie"
> (just an easy way to
> remember the formula). If the current with 12 Volts (one battery) is
> 1.2 Amperes, we
> would calculate the power to be 14.4 Watts (Watt is another persons
> name just as Volta
> and Ampere are). Now let's again increase the voltage by adding a
> second battery
> which we have already discovered increases the current flow. 24
Volts
> times 2.4
> Amperes gives us 57.6 Watts. That is four times the wattage increase
> for just twice the
> voltage increase. Now you know why some devices get so hot so
quickly.
>
> END
>
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