Electricity 101 Part 1: Voltage and Amperage


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Electricity 101 Part 1: Voltage and Amperage

Postby WingAdmin » Wed Oct 30, 2013 9:27 pm



I see a lot of people who seem to be afraid to touch the electrical parts of their bikes - and to me, that's the easiest thing to fix. A lot of the fear is based on a lack of knowledge. Let me try to help.

Part 1: Voltage and Amperage

This voltage and amperage stuff is simple if you equate it to water: voltage = water pressure, amperage = water volume.

In order to move a large volume of water, you need a big pipe (i.e. a thick wire). On the other hand, you can have any amount of pressure (voltage) you want, regardless of pipe (wire) size. You can put 10,000 psi of water pressure into a pipe the size of a straw. Similarly, you can put 10,000 volts of electricity into a wire the size of a human hair. Of course, if the wall of the pipe isn't strong enough to contain 10,000 psi of pressure, it will rupture, and water will spray out. Similarly, if the thin wire doesn't have strong enough insulation, voltage can "spray" through the insulation and arc (a big spark) to a nearby grounded point.

But for this example, let's say we have a standard 3/4" household water pipe. We have 12 psi of water pressure behind it, and it is capable of moving a volume of 20 ounces of water per second. At the end of the pipe is connected a small water-driven turbine wheel. This turbine wheel, at maximum capacity, can utilize 15 oz of water per second. In the middle of the pipe is a valve, which is turned off. The pressure is still 12 psi, and the volume is zero, because no water is flowing.

Water and turbine - closed valve
Water and turbine - closed valve


Then the valve is opened wide, so there is no restriction. Water flows into the turbine at 15 oz per second, because that is the maximum capacity that it can consume. Because we are not utilizing the full capacity of the water supply, the water pressure remains very close to 12 psi, and there is excess volume capacity.

Water and turbine - open valve
Water and turbine - open valve


Now let's put a second turbine on the end of the pipe, in addition to the first one. The two turbines combined can utilize 30 oz of water per second. However, the water supply is only capable of supplying 20 oz per second. As a result, each turbine gets only 10 oz per second. Another important thing happens: the water pressure DROPS. The full 12 psi of water pressure is only available when NO water is being consumed. As more and more water is being consumed, the pressure available to push it through the pipe drops slightly. When we get to the point where the devices consuming the water can consume more water than can be supplied, the pressure drops dramatically.

Water and two turbines - open valve
Water and two turbines - open valve


Now let's close the valve halfway. The volume of the water drops to 10 oz per second, because that is all the valve will allow through. The turbines are still demanding 15 oz per second each - but now they are each only getting 5 oz per second - which might not even be enough to spin them. The water pressure in the pipe between the valve and the turbines will be getting close to zero.

Water and two turbines - semi-closed valve
Water and two turbines - semi-closed valve


Next, let's look at this exact same scenario, as it applies to electricity:

Instead of a water pipe, we have a 14 gauge wire. Instead of 12 psi of water, we have a battery, supplying 12 volts of electricity. Instead of a capacity of 20 oz per second of water, the battery is capable of supplying 20 amps of electrical current. At the end of the wire, is connected a small electric motor. This motor, when under full load, can draw 15 amps. In the middle of the wire is a switch, which is turned off. There is still 12 volts available, but the amperage is zero, because no current is flowing.

Then the switch is turned on, so there is no restriction. Electricity starts flowing into the electric motor at 15 amps, because that is the maximum current that it can draw. Because we are not utilizing the full capacity of the battery, the voltage remains very close to 12 volts, and there is excess current capacity.

Now let's put a second electric motor on the end of the wire, in addition to the first one. The two motors together can draw 30 amps of current. However, the battery is only capable of supplying 20 amps. As a result, each motor draws only 10 amps. Another important thing happens: the voltage DROPS. Full voltage is only available when NO power is being consumed. As more and more power is being consumed, the voltage available to push it through the pipe drops slightly. When the devices consuming the power can consume more current than can be supplied, the voltage drops dramatically.

Now instead of a switch, let's put a resistor - which is the same as a partly-closed valve. The current flowing in the wire drops to 10 amps, because that is all the resistor will allow through. The electric motors are still requiring 15 amps each - but now they are each only getting 5 amps - which might not even be enough to spin them under load. The voltage between the resistor and the motors will be getting close to zero.

You can see the parallels. In the real world, instead of a resistor, it could be a frayed wire, a dirty connector, a corroded terminal, or any of a number of other things that impede the flow of electricity. One other thing happens: the thing impeding the flow heats up, from friction. This actually happens in the water valve as well, but it's practically undetectable, because the water flow carries the heat away. In the electrical world, the resistor (or connector, or wire) heats up. And as the resistor heats up, it starts resisting the flow of current even more. A good example of this is the infamous "three yellow wires" connecting the stator to the rectifier in our four-cylinder Wings. The connectors get dirty, and start acting as a resistor. As a result, they heat up, and eventually get hot enough to melt the connectors.

Let's look at it as it applies to the starter motor. You have a battery, supplying 12 volts, and capable of supplying 300 amps (for short bursts). You have a wire going through the solenoid (essentially just a switch), and then to the starter motor, which can consume lots of amps (I don't know the exact amount, let's say it's 200).

You hit the starter button, it closes the solenoid, allowing the current to flow to the starter. It, under load (because it's turning the engine), draws 200 amps, and everything is fine.

However, now let's say the solenoid is faulty - it is acting as a resistor. It is restricting the amount of current available to the starter to say, 150 amps. Because the starter is demanding 200, and only 150 is being given to it, the voltage drops considerably. If you attach a voltmeter, you will see close to a full 12 volts BEFORE the solenoid, and something more like 6 or 7 volts AFTER the solenoid. Now you know the solenoid is the problem.

And as to why a free-spinning starter tells you nothing? Electric motors draw almost nothing when run with no load. They draw the MOST current when they are stopped dead. The faster they spin (meaning the less load they have to turn), the less current they draw. So if you hook up your free-spinning starter to your starting system, press the button, and everything sits happily at 12 volts - well, that's because the starter is only drawing 5 amps of current, well within the capacity of whatever the thing is that is acting as a resistor (in our example, the solenoid).

And lastly, why should you not run your starter for more than a few seconds when starting your motorcycle? The windings (coils of wire) inside it, that act as a giant electromagnet, causing it to spin - are basically one giant resistor. And remember what happens to resistors when a lot of current is being pulled through them? They get hot. And in this case, we're talking 200 amps, which is an enormous amount of current, so your starter gets very hot, very fast. Give it some time to cool off before trying again.



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Re: Electricity 101

Postby dadztoy » Thu Oct 31, 2013 3:27 am

Nicely done Admin - pretty much the same way I learned my electronic theory 45 + years ago... All still holds true today... Can hardly wait for part 2. :-)

Les

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Re: Electricity 101

Postby virgilmobile » Thu Oct 31, 2013 9:49 am

If I'm allowed..I'll add a little too....If not..by all means...delete this post...

The common idea is the "red" wire is the "hot" wire....In DC electronics reality,, it is not...
Electricity(moving electrons) is provided from the negative terminal of the battery...The electrons actually flow through the frame to all the individual grounds,into the "load"..(ex.light bulb) and then return to the positive lug of the battery....

The main reason to ensure all the "grounds" are clean and tight....There the source of the "power" needed to operate the load....

One other thought...electrons travel best on the surface of a conductor,not up the middle...So in reality a #12 solid copper wire will carry less "power" than a #12 fine stranded copper wire...
Strange but true...the #12 fine strand wire has much more surface area for the electrons to travel on....
Negative(ground)= excessive electrons
Positive(hot)= lack of electrons
Electrons travel from negative to positive to complete the circuit...

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Re: Electricity 101

Postby WingAdmin » Thu Oct 31, 2013 11:27 am

Virgil, I was kind of expecting (and hoping) that you would contribute! :)

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Re: Electricity 101

Postby virgilmobile » Thu Oct 31, 2013 12:34 pm

What a nice surprise to actually hear that others are willing to learn about this magic some take for granted and understand...

I read too often of owners spending there gas money on parts to try and fix something when just a basic understanding of electric and the meters would have narrowed the problem...

Maybe a electricity 102 tutorial of basic test equipment and readings.....
With cheap Walmart/Harbor Freight stuff that anybody can get...
How and when to use (or not use) a DVM,Analog volt meter,Test probe..
Why use one rather than another,etc...

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby Seoladh » Wed Feb 19, 2014 3:52 pm

Thanks, I consider myself to be a educated novice on electrical knowledge, but always need and want to see more information. Thanks for 101 and will continue to read more.
Ride safe & forever,
Seo

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby VatosPapa » Tue Dec 30, 2014 2:40 pm

Thanks you guys. I am one of the intimidated ones when it comes to electricity. Its just like you said, if somebody doesn't understand something its easy to be afraid of it.

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby Ol' Man » Tue Dec 30, 2014 10:49 pm

I'm likin' where this is going. 8-)
even if it is a year old. :oops:
Today is the oldest you've ever been,
yet the youngest you'll ever be,
so enjoy this day while it lasts.

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Re: Electricity 101

Postby Sawdust62 » Sun Jun 21, 2015 9:05 pm

virgilmobile wrote:If I'm allowed..I'll add a little too....If not..by all means...delete this post...

The common idea is the "red" wire is the "hot" wire....In DC electronics reality,, it is not...
Electricity(moving electrons) is provided from the negative terminal of the battery...The electrons actually flow through the frame to all the individual grounds,into the "load"..(ex.light bulb) and then return to the positive lug of the battery....

The main reason to ensure all the "grounds" are clean and tight....There the source of the "power" needed to operate the load....

One other thought...electrons travel best on the surface of a conductor,not up the middle...So in reality a #12 solid copper wire will carry less "power" than a #12 fine stranded copper wire...
Strange but true...the #12 fine strand wire has much more surface area for the electrons to travel on....
Negative(ground)= excessive electrons
Positive(hot)= lack of electrons
Electrons travel from negative to positive to complete the circuit...


I just finished a class on physical science for my B.S. degree, and can’t resist adding to this thread what I’ve learned.
The reason current (electrons) flows from a battery’s negative terminal to the positive terminal is because of the atoms in the battery. An atom is made up of three primary parts: a neutrally charged neutron, a positively charged proton, and negatively charged electron. When an atom has more protons (+) than electrons (-), it is said to have a positive charge. So the positive post of the battery has many many positively charged atoms or molecules that have more protons than electrons. The negative post has atoms that have more electrons (-) than protons (+). When you connect the two posts together, through a light, motor, or other load, the electrons in the negative side try to return to a neutral state by moving their excess electrons to the positive post’s atoms that are lacking electrons. In other words, the atoms try to balance the number of protons and electrons of both sides until they are no longer charged positive or negative. Once this happens, the battery is dead, or has no charge, so current (electron) flow stops.

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby BikerBuck » Tue Jun 30, 2015 7:11 am

My understanding of current flow was negative to positive with in the battery (ie negative plate to positive plate). Therefore outside the battery current flows from the positive terminal and returns to the negative terminal. Current flows to the load and then to ground which is the frame. Please correct me if I'm wrong.

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby BikerBuck » Tue Jun 30, 2015 11:10 am

I stand corrected. After reading up on battery physics, Virgil is right on! If you really want to confuse yourself read up on conventional flow notation vs current flow notation. It will take you back to Ben Franklin days and a half hour of your day you'll never get back. Virgil, You the Man!

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby OmegaTech » Mon Jul 27, 2015 8:11 am

How to put someone OFF testing electrical systems. Having been in the electrical Industry for over 40 years here is the simple explanation

Actual current flow(electrons) goes negative to positive. No one should use this theory

Conventional current flow goes positive to negative, everyone should use this.

Batt+ve. -------------> Switch -----------> Load ----------> Batt -ve (or Frame)

Ian, London (UK)

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby Blackngold » Sat Dec 05, 2015 12:18 pm

So which way does lighting flow? Ground to sky, or sky to ground? Where is the conductor,resistance,battery(source)? How did ole Ben Frank not get electrocuted when flying that kite?(no rubber shoe soles) If wood is a bad conductor then why do they say don't stand under a tree in lighting storm? The ponderings of a bored mind :roll:

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Re: Electricity 101 Part 1: Voltage and Amperage

Postby WingAdmin » Mon Dec 07, 2015 10:56 am

Blackngold wrote:So which way does lighting flow? Ground to sky, or sky to ground? Where is the conductor,resistance,battery(source)? How did ole Ben Frank not get electrocuted when flying that kite?(no rubber shoe soles) If wood is a bad conductor then why do they say don't stand under a tree in lighting storm? The ponderings of a bored mind :roll:


Everything is a conductor. Just some substances are a much better conductor than others. Air is a very poor conductor, but if you get the voltage high enough, it will conduct - and the result is a spark (or a BIG spark, otherwise known as lightning). Wood is a bad conductor, but much better than air, so lightning will prefer it (lightning will search out the shortest path to ground, so if a tree makes that path shorter by 30 feet, it will pick that tree). Wet wood is a much better conductor than dry wood. In fact, wet anything is a fairly decent conductor, because water is a reasonable conductor as well. Salty water is an excellent conductor, which is why salt water causes rust - rust is an electrical process.

Your body is primarily a bag full of salty water, which makes an EXCELLENT conductor. So don't stand out in a field in a lightning storm.




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