circuits

circuits - Circuits Current Resistance & Ohms...

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Unformatted text preview: Circuits Current Resistance & Ohms Law Resistors in Series, in Parallel, and in combination Capacitors in Series and Parallel Voltmeters & Ammeters Resistivity Power & Power Lines Fuses & Breakers Bulbs in Series & Parallel Electricity The term electricity can be used to refer to any of the properties that particles, like protons and electrons, have as a result of their charge. Typically, though, electricity refers to electrical current as a source of power. Whenever valence electrons move in a wire, current flows, by definition, in the opposite direction. As the electrons move, their electric potential energy can be converted to other forms like light, heat, and sound. The source of this energy can be a battery, generator, solar cell, or power plant. Current By definition, current is the rate of flow of positive charge. Mathematically, current is given by: I = q t If 15 C of charge flow past some point in a circuit over a period of 3 s, then the current at that point is 5 C/s. A coulomb per second is also called an ampere and its symbol is A. So, the current is 5 A. We might say, There is a 5 amp current in this wire. It is current that can kill a someone who is electrocuted. A sign reading Beware, High Voltage! is really a warning that there is a potential difference high enough to produce a deadly current. Charge Carriers & Current A charge carrier is any charged particle capable of moving. They are usually ions or subatomic particles. A stream of protons, for example, heading toward Earth from the sun (in the solar wind) is a current and the protons are the charge carriers. In this case the current is in the direction of motion of protons, since protons are positively charged. In a wire on Earth, the charge carriers are electrons, and the current is in the opposite direction of the electrons. Negative charge moving to the left is equivalent to positive charge moving to the right. The size of the current depends on how much charge each carrier possesses, how quickly the carriers are moving, and the number of carriers passing by per unit time. wire electrons I protons I A circuit is a path through which an electricity can flow. It often consists of a wire made of a highly conductive metal like copper. The circuit shown consists of a battery ( ), a resistor ( ), and lengths of wire ( ). The battery is the source of energy for the circuit. The potential difference across the battery is V . Valence electrons have a clockwise motion, opposite the direction of the current, I . The resistor is a circuit component that dissipates the energy that the charges acquired from the battery, usually as heat. (A light bulb, for example, would act as a resistor.) The greater the resistance, R , of the resistor, the more it restricts the flow of current....
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This note was uploaded on 11/17/2011 for the course PHYS 121 taught by Professor Burgeson during the Fall '11 term at BYU.

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circuits - Circuits Current Resistance & Ohms...

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