Whether it is the static electricity that comes off your clothes out of the dryer, to the giant displays of lightning in thunderstorms, people have been fascinated by electrical charge for millennia.
It was the Greeks who noted the idea of static when they rubbed amber on their clothes, to produce the characteristic effects of attraction and repulsion. The Greek word for amber is ελεψτρον (electron)
But what is charge? It was only in the last 300 years also that we developed a better understanding of electrical charge. Nonetheless, even today, we know materials can possess charge, but at best we are simply describing how it behaves, not what causes electrical charge at the fundamental level.
We will start in the series of lessons about what charge is and how we describe it and explain its behaviour. In subsequent lessons we will look at systems where the charge is moving consistently such as in electrical circuits. Then later we will look at how electrical charges behaves in various fields such as electric fields and magnetic fields.
It was the Greeks who noted the idea of static when they rubbed amber on their clothes, to produce the characteristic effects of attraction and repulsion. The Greek word for amber is ελεψτρον (electron)
But what is charge? It was only in the last 300 years also that we developed a better understanding of electrical charge. Nonetheless, even today, we know materials can possess charge, but at best we are simply describing how it behaves, not what causes electrical charge at the fundamental level.
We will start in the series of lessons about what charge is and how we describe it and explain its behaviour. In subsequent lessons we will look at systems where the charge is moving consistently such as in electrical circuits. Then later we will look at how electrical charges behaves in various fields such as electric fields and magnetic fields.
1. An introduction to Electric Charge
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electroscope
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Starting with a historical overview of our understanding of electrical charge. this video examines the basis of electrical charge, namely the electron and the proton. It's only also examines one of the conservation laws, concept of conservation of charge |
electroscope
Here are two demonstrations that are done in the classroom. They demonstrate the conservation of charge. The first examines how an electric scope works, using the principles of attraction and repulsion, and the movement of electrical charges as a result.
The second video is similar but demonstrates again the conservation of charge. Since only some charges are transferred to a material, the rod and the cube may at some point have the same charge, and at other points have different charges. This results in different behaviours
The second video is similar but demonstrates again the conservation of charge. Since only some charges are transferred to a material, the rod and the cube may at some point have the same charge, and at other points have different charges. This results in different behaviours
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In this video I discuss how ultimately a charge is determined by the number of electrons and protons present in the material. The presumption is that electrical charge at a fundamental level is discrete, based on the number of protons and electrons.
However this is problematic.
Electrons, based on the standard model are a fundamental particle. That is, they are indivisible and so if we assign a discrete value to charge we often assign it with a -1. Consequently, we assign a +1 charge to the proton. Therefore in a neutral atom, we have the same number of protons and electrons.
But protons are not fundamental particles. According to the Standard Model, protons are particle groups, made up of quarks, two up quarks and one down quark. As a result the up quark has a charge of +2/3, and the down quark has a charge of a -1/3.
So although charge is a discrete value, the values of +1 and -1 arbitrary.
You can see more on the standard model here
However this is problematic.
Electrons, based on the standard model are a fundamental particle. That is, they are indivisible and so if we assign a discrete value to charge we often assign it with a -1. Consequently, we assign a +1 charge to the proton. Therefore in a neutral atom, we have the same number of protons and electrons.
But protons are not fundamental particles. According to the Standard Model, protons are particle groups, made up of quarks, two up quarks and one down quark. As a result the up quark has a charge of +2/3, and the down quark has a charge of a -1/3.
So although charge is a discrete value, the values of +1 and -1 arbitrary.
You can see more on the standard model here
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2. Coulomb's Law Explained
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We say electrical charges that are opposite attract and like charges repel.
The correct terminology however, is that a force is exerted on each object with charge. That means this force can be measured. This also means there must be a relationship between the force that is exerted on the charges and the displacement between them What is the relationship between their magnitude and their displacement? This video examines this and it is referred to as Coulombs Law. Wxamine the work solution, the interactive that allows you to deepen your understanding, and attempt some problems as well. |
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Similar to the animation on Law of Gravitation, this pHET animation allows you to explore Coulomb's law
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3. Understanding Electric Fields
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The concept of fields is paramount in physics. This video examines electric fields and how we represent them. |
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play electric hockey
This fun activity requires you to score hockey goals using your understanding of electric fields. Level one is easy, but three is a challenge!
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This pHET animation allows you to explore the nature of fields
4. Understanding Voltage
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Many have an incorrect understanding of voltage, not helped by popular press.
In the strictest sense voltage is about energy of position. If we place an electrical charge in an electric field, it will have a certain energy value. If we move that charge against or with that electric field, that value changes and so we have a difference between the two positions This is the idea of potential difference or more commonly known as voltage. This value is independent of the charge you are moving. This video starts by employing a simple analogy of lifting a mass, and then elaborates on the concept of voltage. |
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5. The plasma ball
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The plasma ball if a great 'toy', that relies on the concept of electrical charges, electric fields and voltage. There are many videos that demonstrate some cool tricks you can perform with it, but not many discuss the physics principles behind it's working. So this video can help consolidate your understanding of electrostatic behaviour. Do you check out my demos video if you want to see some cool tricks. |
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Own or have access to a plasma ball. I go through some great demos that cover physics concepts. |
