Transcript Electricity
Electricity Current and charge Electricity • The flow of an electrical current • Electrons flowing from a negatively charged area to a positively charged area Conductors • Some elements will allow electrical current to flow easier than others. • Materials which easily allow the flow of electric current are called CONDUCTORS . • Conductors have a lot of free electrons that are able to be stripped away and flow easily • Ex: Gold, Silver, Copper, Aluminum, Zinc, Carbon, Salt Water, & wet ground Insulators • Other elements do not allow electrical current to flow easily, and these are called INSULATORS. • Tightly bound electrons that can’t be stripped away easily • Some examples of good insulators are Quartz, Plastic, Rubber, Glass, Polystyrene, and Water. (Yes, water is an insulator.... not a conductor.) Resistors • Electricity, according to Benjamin Franklin, acts like a fluid. • It flows and has a measurable CURRENT . • We can restrict its flow by adding electrical friction. • We say that the restriction of electrical flow is called RESISTANCE and that a device which causes such RESISTANCE is called a RESISTOR Resistance • There are 4 factors that determine the resistance of a material: – (1) Type of Material – (2) Length – (3) Size – (4) Temperature • Resistance then, is basically a form of friction which restricts the flow of an electrical current. Electric current and voltage difference • Electric current – Net movement of electric charges in a single direction. – Measured in amperes.(amps) • Voltage difference – Measured in volts. – Voltage flows from high voltage to low voltage. – High Potential Energy Source to low Potential Energy Electric Circuits • Must have a closed path for current to flow. • A closed complete circuit allows electrical current to flow. • 2 types of circuits series and parallel. Series circuit • A series circuit has more than one resistor and gets its name from only having one path for the charges to move along. • Charges must move in "series" first going to one resistor then the next. • If one of the items in the circuit is broken then no charge will move through the circuit because there is only one path. • There is no alternative route. Series circuit • Old style electric holiday lights were often wired in series. • If one bulb burned out, the whole string of lights went off. Parallel circuits • A parallel circuit has more than one resistor and gets its name from having multiple (parallel) paths to move along . • Charges can move through any of several paths. • If one of the items in the circuit is broken then no charge will move through that path, but other paths will continue to have charges flow through them. Parallel circuits • . Parallel circuits are found in most household electrical wiring. • This is done so that lights don't stop working just because you turned your TV off. Drawing Circuits • Wire • Power Source • Resistor • Switch Open • Switch Close Power sources and batteries • Dry cell batteries – Consists of 2 electrodes and an electrolyte. – The electrolyte allows charges to cross from one electrode to the other. – 1 Electrode is made of carbon the other is made of zinc. – As the battery is used the carbon rod becomes positive( the end of the battery that sticks out) and the zinc becomes negative. Dry cells Types of dry cells Wet cell and Lead –acid batteries • Wet cell – Has 2 connected plates made of metal that sits in a conducting solution. Wet cell construction How do we generate electricity? • Electricity is produced at a an electric power plant. • Some fuel source, such as coal, oil, natural gas, or nuclear energy produces heat. • The heat is used to boil water to create steam. • The steam under high pressure is used to spin a turbine. • The spinning turbine interacts with a system of magnets to produce electricity. • The electricity is transmitted as moving electrons through a series of wires to homes and business.