 Figure 1. A drawing depicting what an atom looks like. Notice how much more area the electron cloud occupies compared to the nucleus.[1] Show Electrons are negatively charged particles that exist in a cloud around the nucleus of an atom. They are unimaginably small, so small that quantum mechanics is needed to explain their peculiar behaviour, and as far as physics has been able to determine they are a fundamental particle. For the scope of this encyclopedia, it is best to imagine electrons as tiny particles that "orbit" the nucleus of an atom (the other resources below will provide a more advanced interpretation). However, instead of the gravitational force that's responsible for moons orbiting planets, the electromagnetic forces causing the electrons to "orbit" the nuclei. For more on the physics of electrons please see hyperphysics. Some properties of an electron.[2] Note that the electron's radius is so small that no one has been able to detect it, but it's incredibly round: "if the electron was magnified to the size of the solar system, it would still appear spherical to within the width of a human hair.[3]
Electrons and ElectricityElectricity is the flow of electrons through a conductor, usually in the form of a wire, this flow is called an electric current. In order for this flow to occur, electrons must break their atomic bond (electricity is the flow of electrons, not the flow of electrons and the nuclei they happen to be bonded to). Breaking the atomic bond between an electron and its nucleus requires an input of energy which causes the electron to overcome the electromagnetic force constraining it and thus flow freely. This needed energy can be harnessed from a number of different sources, and a few examples are:
Conductive materialAll forms of matter contain electrons, however, the electrons in certain materials are more loosely bound to their nuclei. These materials (known as conductors or metals) require very little energy to create an electric current, because loosely bound electrons require much less energy to overcome the electromagnetic force keeping them in place. What generates electron flow?Electric generators are devices that use the principle of electromagnetic induction—this is the process of moving a conductor through a magnetic field in order to create electron flow. Note: only a relative movement of the conductor and magnetic field are needed, meaning the magnetic field could be moving while the conductor is stationary. When the electrons in the conductor pass through a magnetic field (if the field is strong enough and the conductors relative velocity through the field is fast enough) then the bonds to their nuclei will be broken and a flow will be induced. In order to induce a high level of electron flow a great deal of energy is needed in order to create relative velocity between the conductor and magnets. Chemical reactions inside of batteries also create an electromotive force causing electrons to flow in a circuit. Photons (light energy) can also cause electrons to flow when they strike a photovoltaic cell. External resourcesTo learn more about how electrons form matter with protons and neutrons please see our page on atoms. For deeper physics on the electron please see hyperphysics. For more about how electrons are relevant to chemistry please see UC Davis's wiki. To just play around with different models of electrons around an atom, please see PhET's models of the hydrogen atom. For Further ReadingFor further information please see the related pages below: References
What makes an electric charge move? You know that work has to be done to lift an object because the Earth's gravitational field is pulling the object down. In a similar way work must be done to move a charged particle in an electric field. The amount of work required to move a charge between to points or the work per unit of charge is called the 'electric potential difference' between the two points. The unit of potential difference is called the volt. Potential difference can be either positive or negative depending on the movement of the charge. To move charges we need a device that can do work. Such devices include: batteries, generators, thermocouples and batteries. How do electrons move along a wire? Electrons do not move along a wire like cars on a highway. Actually, Any conductor (thing that electricity can go through) is made of atoms. Each atom has electrons in it. If you put new electrons in a conductor, they will join atoms, and each atom will deliver an electron to the next atom. This next atom takes in the electron and sends out another one on the other side. What is electromotive Force (EMF)? Electromotive force, also called emf (and measured in volts) is the voltage developed by any source of electrical energy such as a battery or generator. It is generally defined as the electrical potential for a source in a circuit. A device that supplies electrical energy is called electromotive force or emf. Emfs convert chemical, mechanical, and other forms of energy into electrical energy. The word "force" in this case is not used to mean mechanical force, measured in newtons, but a potential, or energy per unit of charge, measured in volts. What are Conductors? In metals such as copper, silver and aluminum the electrons are not tightly bound to the atoms. They are called "free electrons". This makes them good conductors. Condu tors are materials that allow electricity to flow easily. When a negative charge is brought near one end of a conductor electrons are repelled. When a positive charged object is placed near a conductor electrons are attracted the the object. ABOVE - COPPER ATOM -- SINGLE VALENCE ELETRON IS LOOSELY BOUND Metals contain free moving delocalized electrons. When electric voltage is applied, an electric field within the metal triggers the movement of the electrons, making them shift from one end to another end of the conductor. Electrons will move toward the positive side. -- Copper is a good conductor because the outer most electrons from the nucleus are weekly bound and repulsive, such that a small perturbance, like a potential difference between two ends of a wire, can knock the valence electrons from an atom free, which then perturb the neighboring valence electrons and so on resulting in a cascade disturbance of moving charges or current throughout the material. The energy required to free the valence electrons is called the band gap energy because it is sufficient to move an electron from the valence band or outer electron shell, into the conduction band where upon the electron may move through the material and influence neighboring atoms. The above following diagram illustrates this concept. What are Insulators? Insulators are materials where the electrons are not able to freely move. Examples of good insulators are: rubber, glass, wood, What is a Battery and How does it Work? A battery converts chemical energy into electrical energy by a chemical reaction. Usually the chemicals are kept inside the battery. It is used in a circuit to power other components. A battery produces direct current (DC) electricity (electricity that flows in one direction, and does not switch back and forth as is with (AC) alternating current). For more information on Batteries see: How does a Battery Work? Generators A generator usually means a machine that makes electrical energy. It has a generator head with wires, spinning inside a magnetic field. The resulting electromagnetic induction makes electricity flow through the wires. Hybrid electric vehicles carry a generator powerful enough to make them go. The biggest generators don't go anywhere; they stay in their power station. Thermocouples Thermocouple, TC for short, is a device that converts heat directly into electricity. A thermocouple can also work in reverse - using an electric current to transform into heat as well as cold. Test your Understanding: |
What is the energy of moving electrons
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