Understanding Electricity….Really. By Dave Bailie www.survivalpuck.com
When it comes to survival, a person with a solid working knowledge of electricity can be a very valuable asset. You might be a bit rusty, here is a little refresher.
Even though electricity plays a huge role in so much of our lives, the average person has little understanding of it. You flip the switch the light comes on, what’s to understand? Other than seeing a spark or a lightning bolt, electricity is invisible, we can’t handle it we can’t hold it in a bottle. We are left with only describing its effects which does make it hard to wrap your head around.
Electricity is just the movement of electrons no more no less. All materials are made of molecules and all molecules are made of atoms. All atoms have electrons orbiting around the center of the atom. When an electron from one atom makes the jump to another atom this is electricity, just electrons moving from one atom to another.
Electricity is pretty easy to understand if we relate it to something we are all familiar with and that’s water. I’m going to use a pump and a hose as an illustration.
Let’s think about a water pump. Pumps have two common ratings, the pressure they can supply the water at in pounds per square inch (PSI) and how many gallons of water they can pump in one minute or gallons per minute (GPM).
Then we’ve got the hose, there are two things to consider, the hose diameter and how long it is.
So let’s say you have a pump that puts out 12 psi of pressure and can pump up to 30 gallons per minute of volume. This pump is hooked up to a 100 foot length of half inch diameter hose. When the pump is running we get 8 gallons per minute of water coming out of the hose. Now how can we change the amount of water coming out of the hose?
One way is to increase the pressure coming out of the pump. If we double the pressure to 24 psi we will get 20 gallons per minute. We have doubled the force pushing the water down the hose so we get twice as much thru that hose. If we cut the pressure in half to 6 psi we will get half the volume or 5 GPM.
Another way is to change the flow is to change the hose diameter, if we go to say a one inch diameter hose this larger hose will have less resistance to the water and we might go from 8 gallons per minute to 12 gallons per minute. If we keep going up in hose size we will hit a point where the pump is putting out its full 30 GPM capacity. At this point we can’t get any more out of the pump and making the hose bigger doesn’t help. Now if we decrease the hose size down to one quarter inch this might knock the flow down to 4 GPM because it’s harder for the pump to push the water thru this small hose.
The last way to change the flow is to change the length of the hose, a shorter hose has less resistance and will flow more GPM then a longer hose. Stick 500 or 600 feet of hose on our pump and the flow might be down to a trickle. In this case almost the pumps pressure got used up trying to push water down this long hose.
All of this is pretty straight forward and easy to understand right? If this example makes sense to you then you already understand how the three basic units of electricity work together. These three basic units are Volts, Amps and Ohms. As you might have guessed electricity behaves much the same as water. Volts are just how we measure that electrical pressure, except this pressure pushes electrons instead of water. Like the PSI output of the pump right? 12 psi= 12 volts got it?
Ohms is how you count resistance to flow, a small diameter hose has higher resistance than a larger diameter hose. Small hose =high ohms and a large hose= Low ohms, less ohms= less resistance= more flow.
Amps are just the volume of electrons that are passing over a certain amount of time just like gallons per minute. One amp is an actual number of electrons flowing past one point on a wire in one second. If I recall the number of electrons in one amp was a number with something like 67 zeroes behind it. I just know it’s a big big number.
Here are some examples to tie these together. Our bodies have pretty high electrical resistance that’s why they don’t make electric wire out of meat. So we can grab hold of both the positive and negative posts on a 12 volt battery and not be shocked. 12 volts is pretty low electrical pressure and our bodies have a lot of resistance to electrical flow or ohms, just like a very small diameter hose. So even though a tiny bit of electricity measured in amps is flowing up one arm and down the other it’s not enough for us to feel it or do any damage. Now if we tried this with a 120 volt battery the electrical pressure would be ten times higher. This higher voltage is pushing those electrons up one arm and down the other with ten times more force so there is ten times more flow or amps. You will be shocked for sure. Generally its somewhere around 48 volts that starts to present a shock hazard. You could call our bodies semi-conductors we don’t flow electrons too well.
Metals like to flow electrons so we call them conductors. Some metals have lower resistance than others which makes them better to use as wire. Gold is best, followed by silver and then copper. Aluminum is good steel is fair.
If you take a piece of wire and lay it across the + and – on a 12 volt auto battery (dead short) it will quickly turn white hot and melt. Wire is a good conductor but not a perfect conductor. The imperfect part that creates resistance turns some of the energy into heat within the wire. It takes a lot of amps flowing to cause this kind of heat. As long as the battery can continue to supply enough amps the wire is going to melt. If you tried the same experiment with a small 12 volt battery say AA sized, you might just get a little spark and I’d be surprised if the wire got hot at all. The little battery will do its best to feed amps through the wire. But it’s too small for the job and cant pump out electrons fast enough to keep the voltage up and it drops rapidly along with the amps. Remember this: it is high amps that cause things to smoke. High amps can be caused by high voltage but more often it’s due to low resistance, some manner of short giving the electricity an easy flowing path.
The big battery can supply much more power than the small battery. Notice this is the first time I’ve used the word power. Power is the bottom line; it takes power makes things happen. Sometimes you just need a little for LED headlamp and some time you need a lot to start an engine. Engine power is measured in horse power. To figure horse power (HP) you need to know two things, how fast its spinning (RPM) and with how much torque or twisting force the engine can maintain while keeping up the spin speed. Electrical power is measured in Watts. Just like horse power you need two things to figure out Watts, they are Volts and Amps. Volts x Amps= Watts simple as that. 746 watts equals 1 horse power.
Consider the 1200 Watt blow dryer you may have in your bathroom. Hard to believe but that blow dryer takes nearly 2 horse power to operate. That’s close to the horse power found on some lawn mowers. It’s kind of incredible that all that power can travel thru the power cord. Let’s do the math; I know the voltage at the plug is 120 Volts so if I divide 1200 watts by 120 volts I find out that we are flowing 10 amps, well within the safe range for the size of the power cord. Now I decide to build a blow dryer to run on 12 volts but still put out 1200 watts of power. If a do the math knowing I only have 12 volts to work with it tells me I need a whopping 100 amps. At this flow of amps your standard size RV battery might run this blow dryer maybe 20 minutes until it was dead. This would require wires about as big around as a pencil to carry that many amps. Not too handy in the bathroom, luckily I checked the math before I started. The original cord would have smoked at 100 amps. As you can see it’s much more practical to get higher power using high voltage rather than higher amps or as more commonly called current.
Notice this is the first time I’ve mentioned current and I did this for a reason. You may have learned that current will travel from positive to negative thru a wire. This is called conventional theory and it’s wrong. Electrons flow from negative to positive. Nothing flows from positive to negative. How you ask can this be. I asked an instructor this question years ago. He gave me some BS explanation that the electrons were flowing one way and the gaps between the electrons were going the other way and that was current. It didn’t seem right to me so I tracked down the answer.
Its Ben Franklin’s fault, he found that rubbing wool and wax would produce a little electricity. He surmised that the electrons were traveling from the wax to the wool. He decided the wax was positively charged with extra electrons and the wool had a shortage of electrons and called it negative. It wasn’t until years later that experiments were able to prove he got it wrong and that electrons really travel from what he called negative to what he called positive. By then it was too late everyone had been using Bens rules and we still use them today. For all intents and purposes it doesn’t really matter. Amps and current are terms used interchangeably.
Hope this helps, if this foray into electricity flies I’ll do a few more and just add to what we learned today. It’s what’s between your ears that will keep you alive.
Dave Bailie is the owner of www.survivalpuck.com – compact survival kits…