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Author Topic: Electric VS Electrostatic. Any difference?  (Read 5548 times)

Offline wanhafizi

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Electric VS Electrostatic. Any difference?
« on: 16/06/2009 07:36:19 »
If it is possible to produce a steady Electrostatic current, can it be used for powering normal electrical devices?

tq


 

Offline syhprum

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Electric VS Electrostatic. Any difference?
« Reply #1 on: 16/06/2009 16:50:12 »
Electrostatic generators such as Wimhurst and Van de Graff generators depending on their size produce voltages in the range of 10Kv to 10Mv at currents up to milliamps.
There are few uses for such power supplies that cannot be better served by more conventional PSU,s.
Van de Graff generators have been used in nuclear research and lightning simulation in the past but I do not think they are still in use. 
« Last Edit: 16/06/2009 16:53:07 by syhprum »
 

Offline wanhafizi

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Electric VS Electrostatic. Any difference?
« Reply #2 on: 17/06/2009 01:23:49 »
So, what's the real difference that made this generators impractical? Is it because of its high voltage, low amperage?

Is there any electronic based generator that can do the same function as Wimhurst and Van de Graff generator? Those things are bulky...
 

Offline Soul Surfer

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Electric VS Electrostatic. Any difference?
« Reply #3 on: 17/06/2009 09:31:15 »
Firstly let me state that there is no fundamental difference between electrostatic processes and electromagnetic processes they all comply with the same physical laws "electrostatic" currents generate magnetic fields and batteries generate electrical fields

The real difference is the amounts of energy that can be generated stored and transferred with electric fields (using capacitors) as opposed to magnetic fields (using coils) with human scale devices, frequencies and normally available materials. The availability of ferromagnetic materials in which the atoms behave cooperatively to store energy is the critical thing for mains and low audio frequencies.

Note the term frequency because ALL generating processes have to use a repetitive or rotary action to generate energy continuously.

Ferroelectric materials that store large quantities of electric charge do exist but are much less common than iron and more difficult to control.

If you use high frequencies capacitors become the best way of storing energy as magnetic fields tend to be rather sluggish to change so modern low energy light bulbs and small power supplies all use capacitors for the storage and transfer of energy at radio frequencies.
« Last Edit: 17/06/2009 09:33:34 by Soul Surfer »
 

lyner

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Electric VS Electrostatic. Any difference?
« Reply #4 on: 17/06/2009 14:01:43 »
When it's not moving anywhere  we call it electroSTATIC and when it's flowing we call it an electric CURRENT. The clue is in the meaning of the two words when used in other contexts.

When you charge up a VDG ball, a small current is flowing onto it, increasing the Potential.  It's only a matter  of words, here. The charge on the ball is said to be static.When some charge leaks away or flows through you, it's a current.

You can store much more energy in properly constructed capacitors which use two plates and a dielectric (insulating layer) between. The 'charge in' the capacitor or the electric energy is in the form of a lot of charge displacement within the dielectric. Each molecule become polarised  (the charge distribution is distorted) as charge flows onto one plate and off the other - there can even be a change of shape of the dielectric (piezo electric effect).
The energy stored is QV/2 where Q is the charge and V is the final voltage across the plates. OR CV2/2 where C is the capacity of the capacitor. Double the volts and you get four times the stored energy - and so on till the dielectric breaks down and it arcs across. If there is no leakage, the energy will stay in there for a long time - hours and hours, sometimes.

Storing energy magnetically is less good value because you need to have a current flowing all the time and, unless you spend money on  running superconductors, the resistance of the windings dissipate the energy.

As SS says, it all depends upon your application. An inductor is a very good way of storing energy to smooth out variations in current supply or demand (it's 'sluggishness' is what does the smoothing out any variations) and can be much better than a 'smoothing capacitor', which achieves, basically, the same end. But, in these cases, the timescales are very short (single cycles of the 'mains' for instance. For more than a few minutes, a battery is still the best way in pretty much every case.
 

Offline syhprum

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Electric VS Electrostatic. Any difference?
« Reply #5 on: 17/06/2009 17:07:31 »
Every CRT TV has a small unit supplying up to 27Kv at about 1 mA these employ ferromagnetic cores and weigh about 500 gms, an electrostatic generator would be much larger and expensive.
 

Offline wanhafizi

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Electric VS Electrostatic. Any difference?
« Reply #6 on: 18/06/2009 08:40:52 »
So, we can make our hair stand up by using electricity just like those electrostatic generator does?
 

lyner

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Electric VS Electrostatic. Any difference?
« Reply #7 on: 18/06/2009 11:06:44 »
Every CRT TV has a small unit supplying up to 27Kv at about 1 mA these employ ferromagnetic cores and weigh about 500 gms, an electrostatic generator would be much larger and expensive.
LOPTs rule! But, even they use a capacitative voltage multiplier stack these days, don't they?
I can't imagine ever incorporating a VDG mechanism inside a CRT box.
However, you'd have a problem producing an electrostatic charge with the voltage equivalent to a VDG with transformers. A Tesla  transformer produces very high voltages but at high alternating frequencies - not static.
 

Offline syhprum

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Electric VS Electrostatic. Any difference?
« Reply #8 on: 19/06/2009 21:04:04 »
Up until about thirty years ago all TV,s used external tripler units but modern TV,s get their EHT directly from the LOPT which seems to be too small to contain a tripler unit.
If you want to get your hair standing on air you can obtain a suitable voltage source from a TV via a string of 50 2 meg Ohm resistors (take care!).
 

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Electric VS Electrostatic. Any difference?
« Reply #8 on: 19/06/2009 21:04:04 »

 

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