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 E out = E 1 +E 2 +E 3 +E… E out = 1.5v + 1.5v +1.5v +1.5v = 6v Amperage does not increase I out = I 1 =I 2 =I 3 =I… I out = 1A

Parallel Voltage is the same as one cell only E out = E 1 =E 2 =E… E out = 1.5v Amperage accrues I out = I 1 +I 2 +I 3 +I… I out = 1A+1A+1A+1A =4A

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