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NEWSCIENCENEWSCIENCENEWSCIENCE Electric circuits Electric currents are caused by voltage, and the voltage in a circuit is caused by the imbalances of charge which are present on the surface of the metal wires. "Static electricity" is what makes circuits operate! Without the "static electricity" supplied by batteries or generators, modern electrical devices could not exist. This shouldn't be a big surprise, since voltage and electrostatics are intimately inter- twined. Here's another way to think about it: when you rub some fur on plastic, you gen- erate many thousands of volts, while com- mon batteries only generate a few volts. But both of these create surface charge imbalances. And both create electrostatic attraction and repulsion forces. attract hair and lint and cause sparks, etc., Electric circuits separated. For example, when adhesive even while it is flowing. This puts us into Electric currents are caused by voltage, tape is placed on an insulating surface and the ridiculous situation of talking about and the voltage in a circuit is caused by the then peeled off, both the tape and the "static electricity" which moves! imbalances of charge which are present on — surface will become electrified. No friction It's unfortunate that the term "static elec- the surface of the metal wires. is required. tricity" has become so widely adopted as "Static electricity" is what makes circuits Another example: when a thin material the name for these phenomena. If it had operate! Without the "static electricity". passes between rollers, sometimes the been called something else—"imbalanced _ supplied by batteries or generators, modern material becomes electrified. The rollers electricity", for example—it wouldn't be electrical devices could not exist. This become oppositely electrified. When nearly as misleading. It's easy to think — shouldn't be a big surprise, since voltage | newspaper passes between rubber rollers in about an imbalance which moves or stays and electrostatics are intimately inter- a printing press, the paper becomes electri- still. twined. fied and later on this can cause problems But it's impossible to visualise an unmov - _ Here's another way to think about it: —_ with cling and sparking. ing substance which flows. And it's even when you rub some fur on plastic, you gen- This situation in a large newspaper press more unfortunate that textbooks have wide- erate many thousands of volts, while com- _ inspired Robert Van de Graaff to design his ly adopted the misleading practice of stat- mon batteries only generate a few volts. famous generator. ing that "static electricity is electricity But both of these create surface charge Friction is not required. However, if one which is static and unmoving". This isa imbalances. And both create electrostatic of the materials is rough or fibrous and lie, and is no less a lie when many text- attraction and repulsion forces. does not give a very large footprint of con- books say the same thing. tact area, then the process of rubbing Reality is not determined by one material upon another can greatly majority vote. No matter how many increase the total contact area. people agree otherwise, the emperor's Friction may also remove thin layers clothes remain missing. of oil or oxide, exposing a more pure What we call "static electricity" also Without the "static electricity" surface beneath. has another name: "high voltage". All supplied by batteries or The peeling tape does not have to be of the familiar electrostatic phenomena rubbed in order to generate charge which we encounter in everyday situa- generators, modern electrical imbalance, but the hair does need to be 1000 volts and ranging upto around | €VICeS Could not exist. bing is no the cause of electrification, 50,000 volts at the most. Electrification can come about purely If it attracts lint or raises hair, it's from contact. definitely over 1,000 volts. Rub a bal- loon on your head, and you generate Voltages and e-fields tens of thousands of volts! This is voltage "Static electricity" involves immense without a current. It's the electrostatic forces which drive voltages. Again, using the example of two Here's a way to think about it: pure elec- the charges through the wires ina circuit. insulating surfaces that are adhered (or tric current involves a current with zero Electric currents are pumped by "static rubbed) together and later pulled away voltage, while pure "electrostatic" phenom- _ electricity". from each other, a very strong "electric ena involve electrical voltages with zero field" appears between them, and it is this current. Scuff your feet on a carpet and Friction doesn't cause electrification e-field that can raise hair, attract lint, etc. you create a voltage difference of many So, "static electricity" is caused by fric- In addition, this e-field is an example of thousands of volts between your body and tion? Wrong! "Static" electricity appears pure voltage, or voltage without current. the carpet. Study "static electricity" and whenever two dissimilar insulating materi- The strength of this e-field is incredibly you study voltage itself. als are placed into intimate contact and _ large when compared to the voltage of bat- It would be wonderful if the term "static then separated. All that's required is the _ teries and of common electronic circuitry. electricity" could be removed from the _ touching. It is many thousands of times stronger, English language and replaced by "high- Chemical bonds are formed when the — sometimes hundreds of thousands of times voltage electricity", or possibly by "sepa- surfaces touch; and if the atoms in one __ stronger. rated charge" or "charge imbalance", or — surface tend to hold electrons more tightly, Everyday "static electricity" involves "the science of electrostatics". that surface will tend to steal charged immense voltages. The tiniest "static Also, charge flow and charge imbalance particles from the other surface spark" is caused by about 1,000 volts. can happen in the same wire at the same immediately as they touch. This causes the Longer duration "car door sparks" and time. surfaces to become oppositely "charged": "doorknob sparks" can involve as much as Therefore, anyone who believes that they acquire imbalances of opposite 10,000 volts. "static" and "current" are two types of polarity. One surface now has more opposite, mutually exclusive electricity will electrons than protons, while the other has Electron build-up forever remain hopelessly confused about more protons than electrons. When the So, is it a case of electron build-up? Not the true nature of any electrical surfaces are later separated, the regions of exactly. It is not a build-up of anything. It phenomenon. opposite charge imbalance also get is an imbalance between quantities of supplied by batteries or : generators, modern electrical It's the electrostatic forces which drive the charges through the wires in a circuit. Electric currents are pumped by "static electricity". Friction doesn't cause electrification So, "static electricity" is caused by fric- tion? Wrong! "Static" electricity appears whenever two dissimilar insulating materi- als are placed into intimate contact and then separated. All that's required is the touching. Chemical bonds are formed when the surfaces touch; and if the atoms in one surface tend to hold electrons more tightly, that surface will tend to steal charged particles from the other surface immediately as they touch. This causes the surfaces to become oppositely "charged": they acquire imbalances of opposite polarity. One surface now has more electrons than protons, while the other has more protons than electrons. When the surfaces are later separated, the regions of opposite charge imbalance also get stronger. Everyday "static electricity" involves immense voltages. The tiniest "static spark" is caused by about 1,000 volts. Longer duration "car door sparks" and "doorknob sparks" can involve as much as 10,000 volts. Electron build-up So, is it a case of electron build-up? Not exactly. It is not a build-up of anything. It is an imbalance between quantities of 42 = NEXUS devices could not exist. www.nexusmagazi ne.com OCTOBER — NOVEMBER 2005