Transcript Chapter 5
Chapter 5 Sources of Electricity Chemical Action Alessandro Volta Invented the electric cell – voltaic cell The term volt Discovered that electrical potential was created when dissimilar elements were placed in a chemical. Chemical Action Dissimilar metals placed in an acid and water solution (electrolyte) This action produces a surplus of electrons and when a load is placed a current will flow. Chemicals are used up therefore cannot be recharged. Primary cell – a cell in which the chemical action cannot be reversed (recharged) Types of Primary Cells Dry cells – electrolyte is a paste Zinc-carbon cell Alkaline cell Mercury cell – 5 times more current than conventional dry cells. Lithium cell Silver oxide cell Secondary Cell Can be recharged or restored Car Battery Rechargeable Batteries Nickel-Cadmium cell Lithium-Ion Specific Gravity – weight of a liquid as it is compared to water. (electrolyte in a battery) Hydrometer – used to measure specific gravity. Lead Acid Cell Combinations of Batteries Series Voltage accrues Eout = E1+E2+E3+E… Eout = 1.5v + 1.5v +1.5v +1.5v = 6v Amperage does not increase Iout = I1=I2=I3=I… Iout = 1A Parallel Voltage is the same as one cell only Eout = E1=E2=E… Eout = 1.5v Amperage accrues I = I1+I2+I3+I… I = 1A+1A+1A+1A =4A out out Series - Parallel Treat each area of the circuit separately, then combine them. Treat these rows as Series Treat whole thing as Parallel Other Sources Photovoltaic – solar cell / photocell Made from crystalline silicon mixed with impurities to form a positive and negative semi-conductor material. When exposed to light an electrical potential is developed. Cells – Modules – Panels – Array Photovoltaic Cell N-type semiconductor P-type semiconductor Other Light sensitive Components Photoresistive cell – light sensitive resistors (varies current based on amount of light) Electricity from Heat Thermocouple – a device used to indicate and control the heat of electronic devices. When two dissimilar metals in contact with one another and are heated, a potential difference is developed. Galvanometer – used to measure very small currents Pyrometer – meter/thermocouple combination Thermopile – group of thermocouples Electricity from Mechanical Pressure Crystal properties Distortion when voltage applied Voltage when pressure is applied Piezoelectric effect – creating electricity by the mechanical distortion of a crystal. Crystal microphones Fuel Cell Potential difference created by hydrogen gas and oxygen gas combining with potassium hydroxide. Theoretically 100% efficient Little pollution Magnetohydrodynamic Power Electricity that is generated when an ionize gas is passed through a magnetic field. Cathode – negative plate Anode – positive plate Generator The production of electricity by the use of magnetism in a mechanically rotating machine. Dynamo