Battery/general electricity misunderstandings

[dhong089]

Hello everyone. I think I have a major misunderstanding about the nature of batteries, and just the basic concept of electricity. I would really appreciate your help in straightening some things out. So I’m just going to leap right into the questions.

1. So a battery emits electrons from one terminal and into the other. The electrons START from the negative side and enter into the positive side… right? On all batteries, the electrons start from the negative (thus the reason why that specific terminal is called “negative”). But why do I keep reading from different places that electrons start from the positive? For example, this is what a specific website states: “The positive terminal of your battery can deliver dangerous amounts of current if it shorts to ground. This can be avoided easily.” (the specific quote is referring to car batteries and how you should always remove the negative terminal first). Isn’t the quote basically saying that the positive terminal emits the electrons?

Overall, I’m just confused with car batteries in general. The term “ground” also confuses me a lot. The automotive world keeps throwing around this term called “ground,” yet I don’t exactly understand what it means. Yes, I did have a basic understanding of the concept of grounding, but once I started getting deeper into the automotive world, I feel like I have no clue what grounding really means. People keep saying how it’s so important to remove the negative terminal first, yet I can’t understand why. Can someone solidify my misunderstandings?

2. Let’s say you have a car battery. If you attach a wire from the negative to the positive, the wire would probably get VERY hot, almost instantly (because there is no load/resistance). Thus, if you accidentally drop a wrench or something and it touches both terminals of the battery, a very dangerous event would ensue. Is my understanding correct?

Assuming my understanding is correct, can someone explain the concept of measuring a battery with a voltmeter? When measuring a battery with a meter, you would have to attach a positive probe to the positive terminal and a negative probe to the negative terminal. By doing this, isn’t the circuit complete? Why shouldn’t the voltmeter spontaneously explode and burst into flames?


3. I was playing with batteries and a small test-light yesterday, and I came across a puzzling event. So let’s say I have 1 AA battery (1.5V), wires, and a test-light. If I attach a wire to the negative side, and let the wire run through a small light, and let the wire connect to the positive (basically a simple circuit), the light will shine.

However, let’s say instead of letting the wire connect to the positive side of the same battery, I let the wire attach to the positive side of a DIFFERENT battery. The result was that the light would not light up. In my understanding, shouldn’t a negatively charged terminal still emit electrons and enter into the positive side? Why does it matter that it’s a different battery?


Whew… so those are my 3 strongest mis-understandings that I cannot solve. Any help would be greatly appreciated… answering these long questions would be a feat in itself!

 

[vk6kro]

“The positive terminal of your battery can deliver dangerous amounts of current if it shorts to ground. This can be avoided easily.” (the specific quote is referring to car batteries and how you should always remove the negative terminal first). Isn’t the quote basically saying that the positive terminal emits the electrons?

Perhaps it is badly worded. A large current will flow if you connect the two sides of a battery together with a low resistance connection.

Whether you regard this as conventional current from positive to negative or electron flow from negative to positive probably doesn't matter when you have to deal with the smoke and flames that result.

The term “ground” also confuses me a lot. The automotive world keeps throwing around this term called “ground,” yet I don’t exactly understand what it means. Yes, I did have a basic understanding of the concept of grounding, but once I started getting deeper into the automotive world, I feel like I have no clue what grounding really means.

In this context, "ground" just means the body of the car. Many parts of the car electrical system use the body of the car as a convenient return path back to the negative terminal of the battery.

When measuring a battery with a meter, you would have to attach a positive probe to the positive terminal and a negative probe to the negative terminal. By doing this, isn’t the circuit complete? Why shouldn’t the voltmeter spontaneously explode and burst into flames?

No, the meter has a very high resistance and draws very little current from the battery.

instead of letting the wire connect to the positive side of the same battery, I let the wire attach to the positive side of a DIFFERENT battery.

Current flows between two points in a circuit if there is a voltage difference between them.
There is a voltage difference between the terminals of a battery, but no voltage difference between the terminals of two different batteries.
The electrons have to complete a path and they can't do this if there is no path for them to travel in.

 

[Jiggy-Ninja]

Hello everyone. I think I have a major misunderstanding about the nature of batteries, and just the basic concept of electricity. I would really appreciate your help in straightening some things out. So I’m just going to leap right into the questions.

Remember, always look before you leap.

Safety first!

1. So a battery emits electrons from one terminal and into the other. The electrons START from the negative side and enter into the positive side… right? On all batteries, the electrons start from the negative (thus the reason why that specific terminal is called “negative”). But why do I keep reading from different places that electrons start from the positive? For example, this is what a specific website states: “The positive terminal of your battery can deliver dangerous amounts of current if it shorts to ground. This can be avoided easily.” (the specific quote is referring to car batteries and how you should always remove the negative terminal first). Isn’t the quote basically saying that the positive terminal emits the electrons?

The equations and theories of electricity were worked out before people even knew electrons existed. At that time, an arbitrary assumption was made that current was caused by positive charges moving from the positive terminal to the negative terminal.

We now know that most electric current is caused by electrons going the opposite way. The funny thing is, it doesn't matter. Whether you assume "conventional current flow" (positive to negative) or "electron flow" (negative to positive), all the math works out the same, as long as you're careful with your signs.

Overall, I’m just confused with car batteries in general. The term “ground” also confuses me a lot. The automotive world keeps throwing around this term called “ground,” yet I don’t exactly understand what it means. Yes, I did have a basic understanding of the concept of grounding, but once I started getting deeper into the automotive world, I feel like I have no clue what grounding really means. People keep saying how it’s so important to remove the negative terminal first, yet I can’t understand why. Can someone solidify my misunderstandings?

Two things can be meant by ground; a common connection (usually connected to the negative battery terminal) or a connection to the actual ground (also called earthing). For automotive circuits, it's the first definition.

In order to cut down on wires, the negative terminal of the battery is connected to the car's frame, and called "ground". Everything that needs to be connected to the negative terminal of the battery is connected to the car's frame, so less wires need to be run through the engine compartment.

Probably the reason the negative needs to be removed first is because it's attached to the frame. There's more danger of inadvertently shorting something to the frame than directly across the terminals. Which brings us to the next question.

2. Let’s say you have a car battery. If you attach a wire from the negative to the positive, the wire would probably get VERY hot, almost instantly (because there is no load/resistance). Thus, if you accidentally drop a wrench or something and it touches both terminals of the battery, a very dangerous event would ensue. Is my understanding correct?

The wrench has very low resistance, so that presents a very large load to the battery, because it let's massive amounts of current flow.

Yes, it's very dangerous. The battery could even explode.

Assuming my understanding is correct, can someone explain the concept of measuring a battery with a voltmeter? When measuring a battery with a meter, you would have to attach a positive probe to the positive terminal and a negative probe to the negative terminal. By doing this, isn’t the circuit complete? Why shouldn’t the voltmeter spontaneously explode and burst into flames?

A wrench has very low resistance. Likely much less than 1 ohm. According to Ohm's law (V = IR), this let's massive amounts of current through, and according to Watt's law (P = IV) massive amounts of power. Hundreds, or even thousands of watts.

A voltmeter, on the other hand, by design has very, very large resistance (as large as can be practically made). A typical $50 meter has 10-20 million ohms of resistance, letting only a small trickle of current through it, and dissipating a very small amount of power (several millionths of a watt at worst).

3. I was playing with batteries and a small test-light yesterday, and I came across a puzzling event. So let’s say I have 1 AA battery (1.5V), wires, and a test-light. If I attach a wire to the negative side, and let the wire run through a small light, and let the wire connect to the positive (basically a simple circuit), the light will shine.

However, let’s say instead of letting the wire connect to the positive side of the same battery, I let the wire attach to the positive side of a DIFFERENT battery. The result was that the light would not light up. In my understanding, shouldn’t a negatively charged terminal still emit electrons and enter into the positive side? Why does it matter that it’s a different battery?

Because there isn't a complete circuit.

Look at this from an atomic perspective. Simplifying the picture a little bit, the world is made of two kinds of charged particles: positive (mainly protons) and negative (mainly electrons). Opposite charges attract each other, likes repel. The electric force is STRONG, trillions upon trillions of times stronger than gravity.

The only reason that this massively powerful force doesn't cause absolute havoc with our world is because the positive and negative charges are very finely balanced, cancelling the forces out on large scales.

Final principle, electrons cannot be created or destroyed, at least not by anything you're likely to get your hands on. The battery doesn't create charge, it just gives energy to already existing electrons and makes them move.

If you pump electrons out of a battery without replacing them, the balance is thrown off and there is an overabundance of positive charges. Positive charge attracts negative charges, so it gets harder and harder to force electrons out. Eventually, that imbalance equals the batteries voltage and no more electrons can flow out.

On the other end, forcing electrons in without removing an equal amount creates an overabundance of negative charge, which repels other electrons from entering.

Because of the sheer strength of the electric force, only a few electrons need to move in order to create an imbalance strong enough to oppose the voltage of the batteries.

Whew… so those are my 3 strongest mis-understandings that I cannot solve. Any help would be greatly appreciated… answering these long questions would be a feat in itself!

Long questions with even longer answers...hope that's enough.

 

[dhong089]

First off, thank you guys so much for taking the time and helping out a confused-kid. However, I must say, I’m still very very confused. Maybe I should stop digging into the deeper things and just get my foundations straight… But anyways, I am still a bit confused.

So from what you guys are both saying… the negative is the ground. That means the electrons flow from the positive terminal to the negative terminal? Is this a true statement? Then is my understanding that electrons start from the negative terminal of any battery, and end at the positive terminal of any battery, a false understanding?

Yes, I understand that it doesn’t exactly matter if you use the conventional theory vs. the electron flow theory… however when it comes to real life situations (in this case, car batteries,) doesn’t it matter?

So the general rule-of-thumb is to always remove the negative terminal first (apparently that’s the case). I still don’t see why that’s a safety precaution though. Simply assuming that electrons flow from positive to negative, if you remove the negative terminal first (apparently the “safe” way), then the electrons that flow out of the positive terminal will have no where to travel through, thus the circuit will be incomplete. But now let’s say you remove the positive terminal first (apparently the “dangerous” way). Still assuming that electrons flow from positive to negative, you would basically eliminate the source of where the electrons are flowing from. Thus, no danger would occur. So why does it matter which terminal you remove first? Breaking off the entrance is pretty much the same thing as breaking off the exit. However, my understanding vs. real-life-rules do not coincide. What exactly is going on?!

Jiggy-ninja, can you further explain (or dumb-down) when you say,

“Probably the reason the negative needs to be removed first is because it's attached to the frame. There's more danger of inadvertently shorting something to the frame than directly across the terminals”

I’m sorry but I can’t really picture what’s going on in my mind! If you remove a terminal from the battery source (either positive or negative), than how can a short occur in the first place?

As for the voltmeter mis-understanding, that makes plenty of sense now!

Jiggy-ninja, your explanation of atomic particles just clicked into my mind. I had to re-read it like 10 times though hahahaha. But it makes sense, in a very vague way!

Anyways, thanks once again for the help. I am still confused with a bit of things… but yet again, this is just the beginning. There will be plenty of time for me to read and research!

 

[Jiggy-Ninja]

First off, thank you guys so much for taking the time and helping out a confused-kid. However, I must say, I’m still very very confused. Maybe I should stop digging into the deeper things and just get my foundations straight… But anyways, I am still a bit confused.

It happens, nothing to do except ask more questions.

It's what I do.

So from what you guys are both saying… the negative is the ground. That means the electrons flow from the positive terminal to the negative terminal? Is this a true statement? Then is my understanding that electrons start from the negative terminal of any battery, and end at the positive terminal of any battery, a false understanding?

Negative is ground by convention.

Electrons flow from negative to positive. In most circumstances this never changes.

However, in most electronics textbooks and schematics, current is shown as the flow of positive charges from the positive terminal to the negative. This is because, as I said, this was assumed to be happening before people knew about electrons. There is no mathematical difference between electron flow an current flow, so there's really no reason to change it, other than it confuses people like you.

Yes, I understand that it doesn’t exactly matter if you use the conventional theory vs. the electron flow theory… however when it comes to real life situations (in this case, car batteries,) doesn’t it matter?

It doesn't matter at all. There is no difference between the two models.

So the general rule-of-thumb is to always remove the negative terminal first (apparently that’s the case). I still don’t see why that’s a safety precaution though. Simply assuming that electrons flow from positive to negative, if you remove the negative terminal first (apparently the “safe” way), then the electrons that flow out of the positive terminal will have no where to travel through, thus the circuit will be incomplete. But now let’s say you remove the positive terminal first (apparently the “dangerous” way). Still assuming that electrons flow from positive to negative, you would basically eliminate the source of where the electrons are flowing from. Thus, no danger would occur. So why does it matter which terminal you remove first? Breaking off the entrance is pretty much the same thing as breaking off the exit. However, my understanding vs. real-life-rules do not coincide. What exactly is going on?!

The battery doesn't just push electrons out pf the negative terminal. It also pulls them into the positive. It's like a normal pump; you get blowing on one end and suction on the other.

If you remove the positive terminal, there isn't a complete circuit and the electrons leaving the negative terminal don't have anywhere to go. So they won't go anywhere. The lines are already packed full of electrons, you can't cram more in there without masive amounts of energy. It'd be like trying to cram yourself into a crowded shopping mall on a busy day; if there's no place for the people to go, you aren't getting in no matter how hard you push.

Happens if you disconnect the negative terminal.

Jiggy-ninja, can you further explain (or dumb-down) when you say,

“Probably the reason the negative needs to be removed first is because it's attached to the frame. There's more danger of inadvertently shorting something to the frame than directly across the terminals”

I’m sorry but I can’t really picture what’s going on in my mind! If you remove a terminal from the battery source (either positive or negative), than how can a short occur in the first place?

A misunderstanding on my part. I forgot that the clip was being removed right from the battery.

This seems to say kinda the same thing I did though: http://www.khamnam.com/hardware/how-to-remove-car-battery-why-battery-negative-terminal-disconnect-first-why-positive-terminal-of-the-car-battery-connect-first/

I am far from an expert on automotive electronics though, so I'll let someone else pick up that question.

Jiggy-ninja, your explanation of atomic particles just clicked into my mind. I had to re-read it like 10 times though hahahaha. But it makes sense, in a very vague way!

It's a great feeling, isn't it. Reread it 10 more times and I'm sure it will make perfect sense!

Anyways, thanks once again for the help. I am still confused with a bit of things… but yet again, this is just the beginning. There will be plenty of time for me to read and research!

 

[dhong089]

I read your reply a while ago, but I stumbled onto another misconception... but thanks for the help so far. Anyways, I just need to get this straight.

1.) Batteries will always flow from Negative to Positive, right? That specifically means that the battery flow will start from the Negative Terminal and end at the positive terminal, right?

2.) I do not know why this seems so confusing... but when someone says "the negative terminal is the ground for the battery..." Does that mean the negative terminal is emitting electrons, or ACCEPTING electrons?

Out of every misconception I have, I think these two are the basis of my misunderstanding. I always understood that Electrons flow from neg. to pos. I also understand that sometimes books/textbooks/etc. may use the Positive-to-negative flow. But I always assumed that in reality, all batteries follow the Negative-to-positve flow. For some reason, it feels like the automotive world is saying that the Positive terminal is the terminal that emits electrons while the negative terminal is the terminal that accepts electrons.

 

[vk6kro]

I read your reply a while ago, but I stumbled onto another misconception... but thanks for the help so far. Anyways, I just need to get this straight.

1.) Batteries will always flow from Negative to Positive, right? That specifically means that the battery flow will start from the Negative Terminal and end at the positive terminal, right?

2.) I do not know why this seems so confusing... but when someone says "the negative terminal is the ground for the battery..." Does that mean the negative terminal is emitting electrons, or ACCEPTING electrons?

Out of every misconception I have, I think these two are the basis of my misunderstanding. I always understood that Electrons flow from neg. to pos. I also understand that sometimes books/textbooks/etc. may use the Positive-to-negative flow. But I always assumed that in reality, all batteries follow the Negative-to-positve flow. For some reason, it feels like the automotive world is saying that the Positive terminal is the terminal that emits electrons while the negative terminal is the terminal that accepts electrons.

You might be looking for problems where there are none.

Electron flow is always out of the negative terminal except when the battery is being charged, when it is the other way around.

Connecting one terminal or the other to the body of a car does not change this. Batteries always work the same way.

The concept of conventional current does not change the electron flow either. It always flows in the opposite direction to electron flow.

There are plenty of genuine concepts you need to learn in electronics and they are a lot more fun than this one.

 

[dhong089]

I definitely agree with you... I've been stumbling over this problem for a while, and I do wish to move on. But a reason why I'm so determined to figure this out is because I need to work on my real car.

My understanding is that electrons flow NEG to POS

But in the automotive world, they say that the NEG is the "ground." I'm being informed that the POS terminal is the terminal that "emits" the electrons, thus working on electrical systems in the car makes it very confusing!

 

[vk6kro]

I doubt that anybody actually said electrons flow from the positive to the negative terminals of a battery, but if they did, they were mistaken. It happens.

Here is a diagram from Wikipedia:

That is one source. Every Physics book you could pick up in a library would say the same thing.

I have never seen an electron and yet I have managed to use them on a daily basis for many years. It doesn't matter which way they flow.

It is time to let go of this and get on with more important stuff.

 

[dhong089]

VK6, it's hard to move on when I'm on shaky ground. I wish to also just forget about this and move on, but how can I, if my foundation is weak?

But according to that wiki diagram, maybe I was confusing electron flow with the "flow of positive charge"? What exactly is this "positive charge"?

Also, I would really appreciate if anyone could just get this straight for me:
When they say that the negative terminal is the ground, what does that exactly mean? When they say the neg is ground, the only thing I can think of is that the negative takes in the electrons.

This kind of stuff goes against with the electron theory flow, thus it confuses me a lot.

Let's take this video for example:


In the last part of the video (start from around 1:05), he clips the test light onto the negative terminal of the battery, and probes the test light onto that switch-thing. He then says that this proves electricity is flowing THROUGH the clutch and INTO the ground. But the negative terminal should emit electrons... right?

It's things like these that confuse me... maybe I'm just confusing everything.

BUT... There's just ONE MAIN THING I DO NOT UNDERSTAND. If anyone can make this clear, I swear, I don't think I'll ever ask this question... ever again!

Everyone in the automotive world keeps stating that the negative terminal is the "ground." Isn't the ground supposed to "take-in" electrons? Can someone please just explain that, instead of telling me to move on?! I beg of anyone's help! : /

 

[vk6kro]

The metal body of a car is not ground. Can you see that it is just a fat conductor just like a piece of wire?

Electrons only flow from one terminal of a battery to the other, not to ground if there is one.

So, it wouldn't matter if I took a wire from one side of the battery (either side, but not both sides) and connected it to a piece of pipe that I had driven into the actual ground. The car would still start and there would be no current flow in the wire.
The car wouldn't be able to go anywhere, though.

Until about 1960, there were cars with positive ground as well as negative ground.
It didn't matter and the cars could even touch each other without any current flow between them.
It just meant that they used the car body as a conductor for the positive or the negative side of the battery.
It meant you had to be careful when jump-starting one car with another.
There were even stories of batteries being fitted the wrong way around and most of the car still worked OK. Now, with cars full of electronics, this would be a disaster.

 

[dhong089]

Yes, that's the way I thought the whole time! Since I knew that electrons flow neg to pos, I saw that the chassis was just like a huge conductor, and all the electronic components receive their power through the chassis (and all the electronic components are then attached to the fuse box and eventually to the positive cable)

Then why do technicians/mechanics/videos/etc. say that the negative terminal is "ground" ? Am I supposed to just ignore this? Are they wrong then?

 

[vk6kro]

Then why do technicians/mechanics/videos/etc. say that the negative terminal is "ground" ? Am I supposed to just ignore this? Are they wrong then?

"Ground" in this sense just means a "common" connection, meaning that the negative terminal of the battery is available anywhere on the body of the car because it is firmly connected to the body of the car.

You still seem to be stuck with the idea that electrons will somehow try to flow to "ground".
That concept is NOT used in Engineering and it really only applies to the static electric charges built up in thunderstorms.
Even then, electrons can flow from ground towards a positively charged cloud just as easily as they can flow the other way from a negatively charged cloud.

 

[dhong089]

Wow, I think I finally get it, thanks for dealing with this vk6kro. Seriuosly, I feel like I can breathe now, hahaha!

 

[triden]

Just to add to the question you had about removing the negative battery wire first when working on your car...

This is because the frame of your car is hooked up to the negative battery terminal. If you were to start loosening the bolt on the positive terminal of the battery and accidentally touched the frame or something else under the hood with your wrench, lots of sparks would fly. You always undo the negative terminal first because if your wrench makes contact with anything else, no current fill flow and you won't blow anything up. You can undo the positive terminal first if you want, but just be very careful!