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184_notes:batteries [2018/01/28 13:41] – [Batteries] caballero | 184_notes:batteries [2018/09/19 17:57] – dmcpadden | ||
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Part of Section 18.4 in Matter and Interactions (4th edition) | Part of Section 18.4 in Matter and Interactions (4th edition) | ||
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===== Batteries ===== | ===== Batteries ===== | ||
- | While a pair of charged plates is easy to think about on a general level, it becomes surprisingly complicated to model at a microscopic level. As electrons move from one plate to the other, the amount of excess charge on each plate decreases, which means that over time, the " | + | While a pair of charged plates is easy to think about on a general level, it becomes surprisingly complicated to model at a microscopic level. As electrons move from one plate to the other, the amount of excess charge on each plate decreases, which means that over time, the " |
Rather than dealing with a constantly changing electron current, we are going to start by thinking about a simpler model - one where we //__assume the electron current is constant__// | Rather than dealing with a constantly changing electron current, we are going to start by thinking about a simpler model - one where we //__assume the electron current is constant__// | ||
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{{youtube> | {{youtube> | ||
==== Chemical Model of a Battery ==== | ==== Chemical Model of a Battery ==== | ||
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A battery is ultimately a chemical separation of charge. The battery consists of two metal plates placed in a salt solution: one metal produces excess negative charges when reacting with the salt solution (leaving the metal positive) and one metal produces negative charge in the salt solution leaving the metal positive. Chemically this is often referred to as a [[https:// | A battery is ultimately a chemical separation of charge. The battery consists of two metal plates placed in a salt solution: one metal produces excess negative charges when reacting with the salt solution (leaving the metal positive) and one metal produces negative charge in the salt solution leaving the metal positive. Chemically this is often referred to as a [[https:// | ||
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==== Mechanical Model of a Battery ==== | ==== Mechanical Model of a Battery ==== | ||
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Oftentimes in circuits, we are less concerned with how the electrons in circuits are produced and are more concerned with what happens to the charges after they are produced. This means we will generally simplify our model of the battery to what we call a " | Oftentimes in circuits, we are less concerned with how the electrons in circuits are produced and are more concerned with what happens to the charges after they are produced. This means we will generally simplify our model of the battery to what we call a " | ||
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==== Symbol for a Battery ==== | ==== Symbol for a Battery ==== | ||
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{{184_notes: | {{184_notes: | ||
When describing circuits, we will often draw out a symbolic representation (called a circuit diagram) of the circuit elements that we can use to think about what is happening to the charges in the circuit. When representing a battery, we will either draw out the mechanical model of the battery (including the positive plate, negative plate, and conveyor belt) as shown above, or we will draw out a simplified version of the battery including a short line for the negative plate and a long line for the positive plate (where the steady state is assumed without explicitly drawing the conveyor belt). You may also see a physical drawing of a battery drawn out (particularly in textbooks) with the positive and negative sides of the battery explicitly labeled. Any of these representations of a battery will work. | When describing circuits, we will often draw out a symbolic representation (called a circuit diagram) of the circuit elements that we can use to think about what is happening to the charges in the circuit. When representing a battery, we will either draw out the mechanical model of the battery (including the positive plate, negative plate, and conveyor belt) as shown above, or we will draw out a simplified version of the battery including a short line for the negative plate and a long line for the positive plate (where the steady state is assumed without explicitly drawing the conveyor belt). You may also see a physical drawing of a battery drawn out (particularly in textbooks) with the positive and negative sides of the battery explicitly labeled. Any of these representations of a battery will work. | ||