In the last issue of GEARS, we

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1 PUSHING ELECTRONS by Steve Bodofsky In the last issue of GEARS, we looked at the structure of atoms, and how that structure either supports or prevents electrical flow, based on the number of electrons in the valence shell the outermost ring of the atom. Atoms with only one or two electrons in the valence shell tend to be good conductors, because those atoms will share their valence electrons more easily. Atoms with seven or eight electrons were usually the best insulators. But what actually gets those electrons moving to create electrical flow? Sure, we know that copper, with only one valence electron, will allow its electron to move easily, but something has to give it that push to get it moving. The question is what? Let s face it: Just because something works as a conductor, that doesn t mean its electrons will always be in motion. If that were the case, every time you picked up a penny, you d get a shock! So what gets those electrons moving in the first place? Well, if you read the article on oxygen sensors in the March 2004 issue of GEARS, you d know there are four common ways of creating electricity: 1. Solar Power 2. Nuclear Power 3. Mechanical Generator 4. Chemical Reaction We can skip solar and nuclear for our discussion; they really don t apply to cars all that often. That leaves us with mechanical or chemical. Both of these methods of generating electricity apply to cars. Alternators are a mechanical type of generator that use a moving Figure 1: You can build your own battery demonstration using a lemon for the acid, and a nickel and a penny for the dissimilar metal plates. magnetic field to push electrons through a circuit. We ll look at this type of electrical generation in more detail later on in this series. For now, we re going to concern ourselves with chemical reaction for creating electricity which takes us right to the car s battery. How Batteries Work Batteries are electrochemical devices; that is, they create electrical flow through a chemical reaction, called electrolysis. Here s how electrolysis works: Two dissimilar metal plates are immersed in an acid solution. When those plates are connected to one another through a circuit, it starts a chemical reaction between the plates. This chemical reaction causes electrons to flow from one plate, through the circuit, to the other plate. You can demonstrate this process yourself, using a lemon, a nickel and a penny (figure 1): Cut the lemon in half. Make two small cuts in the lemon, about half an inch apart. Insert the nickel in one cut, and the penny in the other. Now use your voltmeter to measure the voltage from the battery you ve 36 GEARS July 2005

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3 Electrons In Motion: What Makes Them Move? The battery provides the potential for electricity, just as the cigarette lighter provided the potential for fire. What s missing is the circuit; without a circuit connecting the two terminals, there s no way for the electrons to flow, so there s no voltage. Figure 2: The voltmeter shows the results of your demonstration battery; this one creates a voltage of volts. created (figure 2). As you can see, immersing the two different metal plates the nickel and the penny into an acid solution the lemon is all that s necessary to duplicate the conditions that take place in a standard automotive battery. Of course, the voltage isn t very high; less than volts. To get enough power out of your lemon battery to start a car would require a whole grove of lemons, and several rolls of nickels and pennies. (No, you wouldn t necessarily get more voltage using dimes and quarters!) To create the additional power that a car requires, automotive batteries use a whole series of plates, with far more surface area than a nickel and penny. And they re immersed in an acid that s a lot stronger. The combination gets way more electrons moving than we could with a single lemon and 6 cents in change! Voltage vs Potential Okay, now we re going to sandbag you: figure 3 shows a typical automotive battery. As it sits now, is there voltage at the terminals? If you said that the battery actually provides a voltage potential, well, you re right. But you only get half credit; you ll get the rest if you can explain what voltage potential means. The fact is, there is no voltage at the terminals; at least, not yet. So far all we have is the potential for voltage. But exactly what does that mean: potential voltage? Take a look at figure 4. It s a cigarette lighter. But is it fire? No, of course not. But it does provide the potential for fire. All we have to do is flick our Bic, and presto! we have fire (figure 5). The battery provides the potential for electricity, just as the cigarette lighter provided the potential for fire. What s missing is the circuit; without a circuit connecting the two terminals, there s no way for the electrons to flow, so there s no voltage. But wait: I just checked the terminals, to see if we were right (figure 6). There was voltage showing on the meter! How come? Were we wrong about there not being voltage? No, we were correct; there was no voltage at the terminals until we connected the meter. Connecting the meter to the battery s terminals created a circuit between Figure 3: With the battery as it appears here, is there voltage at the terminals? Figure 4: You probably recognize this as a cigarette lighter. But is it fire? Or simply the potential for fire? Figure 5: To get fire from the lighter, we have to spin the striker and hold the lever. But the lighter provides the potential for fire, just like the battery is the potential for electricity. 38 GEARS July 2005

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5 Electrons In Motion: What Makes Them Move? Figure 6: Sure there s voltage at the terminals now with the meter connected. The meter creates the circuit necessary for the battery to develop electrical flow. them. And that circuit was all that was necessary to start the chemical reaction in the battery, and create electron flow. Here s why: Heisenberg Uncertainty Principle If you re a television watcher, you ve probably heard someone, mention the Heisenberg Uncertainty Principle on one of your shows probably using it in an incorrect context. In United Tranz Core Supplier of Transmissions Hard Parts for Transmissions Torque Converters Transfer Cases Foreign & Domestic Manual & Automatic Before you call the Rest, Call the Best Quality on Transmission parts Extraordinary Service UPS Daily Call, You ll be glad you did Figure 7: Sure, it was a joke that increasing the coin denominations would somehow increase the voltage; in fact, using a dime and a quarter would actually decrease the voltage to almost nothing, because the metals are almost identical. Without dissimilar metals, we don t get the conditions necessary to develop a voltage. fact, in a recent episode of the show Numbers, they used it wrong intentionally, and pointed out the incorrect usage at the end of the show. For those who are unfamiliar with it, the Heisenberg Uncertainty Principle states that it s impossible to know both the location and momentum of a subatomic particle, but it is possible to describe the probability that the particle will be found within a given region. That sounds pretty complicated, and it is, if we were interested in all of the conditions this principle indicates. But what s important to us is what it says about measuring electricity. Remember, electricity is the movement of electrons, and electrons are subatomic particles. What the Heisenberg Uncertainty Principle is saying is that the very act of measuring electricity will change the position and movement of those electrons. This is because to make a measurement, you must disturb the system; in other words to know something is there, you have to bump into it. That s important, because it means that every time you connect a meter to measure the electrical flow in a circuit, you re altering that circuit. And it s why today s meters all have extremely high resistance; usually 10 Megohms or more. The reason? To reduce the effect of the meter on the circuit, and, by extension, it s effects on the electrical flow. But it s still important to recognize that connecting a meter to a circuit will have an effect on the electron flow through that circuit. In some cases, connecting the meter turns a simple circuit into a parallel circuit. In others, it adds a resistance to the circuit. Regardless of how you connect the meter to a circuit, it has to affect that circuit. That s what we learn from the Heisenberg Uncertainty Principle, and what it says about electrical circuits: Connecting a meter to measure electron flow will have an effect on the electron flow. So, to develop electricity through electrolysis in the battery, we need a complete circuit between the two terminals. Until then, all we have is the potential for electricity. In the next issue of GEARS we ll begin to look at circuits: What makes a circuit, and the different types of circuits. And until then, keep on pushing those electrons! 40 GEARS July 2005

6 Electrolysis Can Damage the Cooling System While electrolysis is a necessary condition for creating voltage in a battery, it s also a common cause for damage to the vehicle s cooling system. That s because, over time, acids build up in the cooling system. The acidic coolant connects the entire cooling system: radiator, engine and so on. The problem is, most of today s cars use any number of different types of metal in their cooling systems. Radiators may use copper, brass and even aluminum: all conductive metals. And the engine is usually cast iron, with aluminum or steel in different places. What s more, all of these components are connected, either by being bolted together, or through being mounted to a common ground. So what we end up with is multiple dissimilar metals, bathed in an acid solution, and connected to form a type of circuit. What does that cause? Electrolysis. No doubt, you ve seen the results of that electrolysis over the years. Rusted freeze plugs, eroded intake manifolds, leaking heater valves all common effects of electrolysis taking place through the vehicle s cooling system. How can you prevent this electrolysis? Sure. That s why most manufacturers recommend replacing the coolant every couple years. You can also use an additive to neutralize the acids, and protect the system. But what s important to remember is that while electrolysis is a valuable process inside the battery, it can be a damaging condition in the cooling system. Quiz: Quiz : Q u i z : Q u i z : 1. What conditions make a substance a good conductor? a. 1 or 2 protons in the atom s nucleus. b. 1 or 2 neutrons in the atom s valence ring. c. 1 or 2 electrons in the atom s valence ring. d. 7 or 8 electrons in the atom s valence ring. 2. Technician A says batteries create electricity through a chemical reaction. Technician B says generators create electricity through mechanical generation. Who s right? a. A only b. B only c. Both A and B. d. Neither A nor B. 3. Which of these is necessary for a battery to create electricity? a. acid b. dissimilar metal plates c. a circuit d. All of the above. 4. The process of creating electricity through a chemical reaction is called: a. electrolysis b. electrolyte c. election d. Carmen Electra 5. If there s no circuit connected, how much voltage does a car battery have at the terminals? a volts b. 6.3 volts c. 0.0 volts d. No way to be sure 6. The Heisenberg Uncertainty Principle relates to predicting: a. personal relationships b. subatomic particles c. customer satisfaction d. the stock market 7. The reason the Heisenberg Uncertainty Principle defines our understanding of electricity is because: a. electricity is the flow of electrons. b. electrons are subatomic particles. c. measuring electron flow requires altering the circuit. d. All of the above. 8. If there s no voltage at the battery terminals without a circuit, why does the voltmeter in figure 6 register voltage? a. because the meter creates the circuit. b. because the meter is broken. c. because the meter s hooked up backward. d. because the Heisenberg Uncertainty Principle creates a voltage. 9. Most meters have very high resistances because: a. they cost less to manufacture. b. it makes the meter more accurate. c. it reduces the meter s effect on the circuit. d. it increases the meter s resolution. 10. What would happen with the lemon battery if you replaced the nickel and penny with a dime and a quarter? a. You d get nearly 6 times the voltage. b. You d get 29 cents change. c. You d get almost no voltage, because the metals are the same. d. None of the above. GEARS July