Sources of Electricity Electronics 1 CVSD

Resistance A measure of the opposition to the flow of electrons through a material Unit of Measurement: – Ohm (Ω) Symbol: – R

Voltage A measure of the Electromotive Force that pushes electrons through a circuit (Potential Difference) Unit of Measurement: – Volt (V) Symbol: – E

Current A measure of the Intensity or total amount of electrons flowing in a circuit in a given unit of time Unit of Measurement: – Ampere (A) Symbol: – I

Power A measurement of the rate of consuming energy, transferring energy, or doing work Unit of Measurement: – Watt (W) Symbol: – P

Six Sources of Electricity Chemical Magnetic Friction Pressure Heat Light

Chemical Uses unlike materials (electrodes) in a solution (electrolyte) to form a “voltaic cell” Cell: Two electrodes with an electrolyte in between Battery: Multiple cells strung together in series &/or parallel circuits Primary cell = cannot be recharged Secondary cell = can be recharged Cells can be “wet” or “dry” (refers to electrolyte)

Magnetic Uses a conductor “armature” passing through a magnetic field (lines of flux) As the conductor “cuts” through the lines of flux, a voltage is produced (electrons attracted to or repelled by the field) Used in generators to convert mechanical energy into electrical energy Amount of current produced depends on speed of armature & # of coils in the armature

Friction Electrical charge can be produced from rubbing certain unlike materials together (electrons transfer from one of the materials to the other) Called “static electricity” The release of this “static charge” results in a static shock (lightning, when you shock yourself on metal, etc) Friction between the touching surfaces often causes heat (helps transfer electrons)

Pressure Some materials will transfer an external pressure to their internal atoms, which drives their electrons out of orbit (causing an electric charge) Most common material = crystals Used in microphones and phonograph pickups Convert mechanical energy into electrical energy

Heat Two unlike pieces of metal joined together produce electricity when heated Called a “thermocouple” Current depends on the amount of heat & types of metals used Converts thermal energy into electrical energy Used in conjunction with a ammeter to make a pyrometer (measures high temperatures)

Light When light hits certain materials it releases electrons, causing an electric charge. Main principle behind solar cells (photo voltaic cell) Solar cells are made of silicon, when light waves hit the silicon they release electrons Convert light energy into electrical energy Amount of current depends on amount of light

Review Voltage is: Current is: Resistance is: Power is: What are the six sources of electricity? List the principle parts of a voltaic cell Lightning comes from which source? What is the difference between a primary and secondary cell?