Electricity Basics


Postby DIYvirgin1975 » Sun Feb 03, 2008 4:17 pm

I visited northern India a few years ago and noticed that the electricity goes off for two hours each day in homes. Why is this ?. Most big bussiness nearby have electricity for a full 24 hours.
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Postby kbrownie » Sun Feb 03, 2008 8:55 pm

Hi
I understand that they do this to reduce the countries output of energy, but only to the domestic sector as India is a booming country with regards to industry so they are kept poered up.
KB
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Postby DIYvirgin1975 » Mon Feb 04, 2008 5:18 pm

It is a good way of saving energy. Most houses have a battery back up up to three circuits so when the power cuts off the battery operates with in 10 seconds.

Why doesnt this method be used in the UK ? because it will mean less expensive bills.
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Postby DIYvirgin1975 » Mon Feb 11, 2008 8:56 pm

What voltage and ampage can kill you ?
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Postby ericmark » Tue Feb 12, 2008 3:56 pm

I understand as low as 24 volts if in wrong place can kill but we normally consider 50 volts as the limit except in wet locations were we think of 12 volt being the limit. As to amps it is really the burns that kill rather than current on its own but of course there is a direct link between volts and amps so by limiting the amps one also limits the volts so for example if you feed 230 volts to a one meg ohm resistor then measure the volts at the other end it will still be 230 volts but as soon as it flows through the body the resistance in the body will reduce it to only a few volts.
On your first question if one takes power and stores it then uses it later it uses more power than just using it so to remove the power for set time does not really save energy. On the Falklands 25 years ago they also had power for limited time because generators use fuel even on tick over so all washing and ironing etc had to be done in the morning or evening nothing at night or middle of day.
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Postby stevenc1603 » Tue Feb 12, 2008 4:28 pm

Volts doesn't really matter. A taser passes thousands of bolts but doesn't kill the intended target (usually)

As for amps, less than 1a is enough, so I have been led to believe.
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Postby ericmark » Tue Feb 12, 2008 7:34 pm

As I said volts, amp, and ohms are interrelated so if human body is 200kohms then to push 1 amp through the body will need 200,000 volts which will stop the heart. This is what is done when it is not working correctly so it can restart we see it all the times in films. There is of course a fourth item which has an effect that is time. Again all interrelated watt = joule per second = volts x amps. So not simply one or the other. A car battery can deliver 1000 amps but with only 12 volt if we again consider human body as 200k ohms gives 0.06ma. Of course direction of flow is also important between your hands will go through your heart which is why one is often told to use only one hand. The biggest problem is ionization of the atmosphere should this happen one gets an explosive force which can throw people across rooms which is why all test probes are to be to GS38 which in turn means they are fused so one hopes will not produce the ionization which is so destructive. In short don't touch it bites.
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Postby sparx » Wed Feb 13, 2008 10:40 pm

Hi we where taught "it's the Volts that jolts, it's the mills that kills"
hence the reason for 30mA rcd's. also as stated skin resistance varies current through body, ie from a fixed voltage source very dry skin (like my leathery old mitts) has much higher resistance to current flow than nice soft wet ones (in a manner of speaking), as found after a shower or bath hence 'special locations' regs,
looked at from another way, skin resistance too high for 50Volts to 'drive' enough miliAmps to kill, hence site supplies 50V to earth, hope this helps
regards SPARX
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Postby DIYvirgin1975 » Mon Feb 18, 2008 5:58 pm

So it is the amps that kills. I didnt realise a little as 1 amp kills.

How many volts in 1 amp
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Postby pyro_mania » Mon Feb 18, 2008 10:06 pm

[quote="DIYvirgin1975"]So it is the amps that kills. I didnt realise a little as 1 amp kills.

How many volts in 1 amp[/quote]


I was told at college that 80mA (0.08 amps) can kill.

There are aren't any volts in 1 amp. They're 2 different variables. The volts 'push' the current (amps) through a circuit. The amount of current depends on the resistance as someone has already mentioned in this thread.
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Postby sparx » Mon Feb 18, 2008 11:09 pm

Hi, 0.05A can kill you easily! which is why we go with 0.03A (30mA) rcd's.
1Volt applied to a 1 Ohm resistor will pass 1Ampere, the basis of
'Ohm's law', fortunately our skin resistance is higher than 1 Ohm so needs more volts to 'drive' amps.
depending upon circumstances it is generally accepted that less than 50V will not cause a lethal current to flow thro' normal body resistance of a healthy adult in dry conditions, might stop a 'pacemaker' though!!!
regards SPARX
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