Electricity We know that electricity behaves in a consistent predictable manner, in given situations, but electricity has never clearly been defined. Atoms –neutrons, protons and electrons Atoms are neutrally charged Most of the weight of an atom is found in the protons and neutrons. Protons are more or less attached to the nucleus Electrons revolve around the nucleus like planets revolve around the sun
Electricity Some electrons, particularly in metals are loosely bound and can detach and become “free electrons” Free electrons as the name implies can move freely from atom to atom When a force or pressure is applied free electrons begin to move
Electricity The materials that allow this movement are called CONDUCTORS The three metals that make the best conductors: Silver Copper Aluminum
Electricity Non Conductors or Insulators: Dry Wood Glass Rubber Mica Asbestos Semi-Conductors: Silicon
Electricity Charged Bodies Like charges repel Unlike charges attract
Electricity Electrical energy is transferred through conductors by means of movement of free electrons A material’s ability to conduct current flow determines whether it is a good or bad conductor
Electricity Coulombs Law of Charge The amount of attracting or repelling force which acts between two electrically charged bodies depends on two things: their charges the distance between them Attraction is directly proportional to the product of their charges And indirectly proportional to the square of the distance between them
Electricity The space in and around charged bodies in which their influence is felt is called an Electrical Field of Force or an Electrostatic Field
The force that moves electrons in a conductor can be called VOLTAGE Electromotive Force Difference in Potential
Electricity voltage Current that flows through electrical conductors is directly proportional to the difference in potential Current is directly proportional to the applied voltage Voltage increases – current increases Voltage decreases- current decreases
Electricity voltage Six Methods of Producing Voltage Friction – Static electricity Pressure – Compression of crystals Heating – In copper electrons move away from the heat. In iron they move to the heat. Light – Photoelectric cells Chemical Action - Batteries Magnetism
Electricity Static Electricity When an atom looses zero or neutral charge it becomes either positively or negatively charged. When a material becomes charged it will keep its positive or negative charge as long as it stays isolated from other materials “Static Charge” Once it comes in contact with another material the negative charge will flow to the positive
Electricity voltage Chemical Production of voltage – that’s how batteries produce voltage
Magnetism – a substance is said to be magnetic if it attracts substances like iron, steel, nickel or cobalt Three types of magnets: Natural magnets - minerals like magnetite Permanent magnets - bars of hardened steel that have been magnetized Electromagnets - soft iron core wound with coils of insulating wire Electricity magnetism
Domain Theory of Magnetism – A substance becomes magnetic when there is an unequal number of electrons spinning in opposite directions. When a number of such atoms are grouped together as in an iron bar there is an interaction between the magnetic forces in various atoms The magnet force field around one atom affects adjacent atoms thus producing a small group of atoms with parallel magnetic fields
Electricity magnetism Iron for example has 26 electrons – 15 rotate in one direction and 11 in the other, which causes a tiny magnetic field. When these atoms group together their poles become aligned in the same direction This cluster is called a “Domain” One cubic mm of Iron can contain 10 million magnetic domains
Electricity magnetism Domains are oriented randomly within the iron bar until an external magnetic field is applied When this happens the domains orient themselves with the magnetic field
The battery drives the ring of charge into motion, the charge moves along like a drive belt, and the light bulb filament “rubs” against the moving charge which makes it glow white hot.
Electricity charge The higher the amperage the faster charge stuff moves The more charge stuff that flows (though a larger wire) the higher the amperage A fast flow through a narrow wire can have the same amps as a slow flow of charge through a bigger wire. If you keep the speed constant and increase the size of the wire you also increase the amperage
Electricity watts Watts is the name given to electrical flow – but what flows? Energy Energy is measures in joules A joule of electrical energy can move from place to place along the wires. The amount of energy that flows in one second is one watt
Electricity btu’s Short for British thermal unit, an British standard unit of energy. One Btu is equal to the amount of heat required to raise the temperature of one pound of liquid water by 1 degree Fahrenheit at its maximum density, which occurs at a temperature of 39.1 degrees Fahrenheit. One Btu is equal to approximately 251.9 calories or 1055 joules. As a rough guide, 1 joule is the absolute minimum amount of energy required (on the surface of Earth) to lift a one kilogram object up by a height of 10 centimetres.
Electricity closed circuits A closed loop of wire is not necessarily a circuit unless voltage is present. In any electric circuit where electrons move around, three things are present: Voltage Current Resistance
Electricity closed circuits The physical pathway for current flow is actually the circuit and it’s resistance controls the amount of current flow around the circuit. By knowing any two of the three quantities, the third can be calculated.
Electricity ohms law Ohms Law – The current in a circuit is directly proportional to the applied voltage and indirectly proportional to the circuits resistance. I = current measured in amperes (amps) E = Voltage R = Resistance in Ohms
Electricity ohms law Another way of writing ohms law:
Electricity watts Power pertains to the rate at which work is being done. Work is done whenever a force causes motion i.e. when voltage causes electrons to move in a circuit work is done The rate at which this work is done is called the electric power rate and is measured in WATTS
Electricity watts power Watts = the amount of voltage across a circuit x the current through the circuit or Watts = Volts x Amperes. or P= EI
Electricity circuits Four types of circuits General Lighting Small Appliance Individual Appliance Ground Fault Circuit Interrupter
Electricity circuits General Lighting One 15 amp circuit per 600 square feet Rule of thumb – 12 outlets Or one 20 amp circuit per 800 square feet Rule of thumb – 16 outlets Lights in kitchens and baths must be permanently wired.
Electricity circuits Small Appliance Circuits serve receptacles for plug-in appliances such as toasters, blenders and coffee makers. The Code requires two 20 amp circuits in the kitchen and one or more in the pantry and dining or family rooms. These circuits may not be used for lighting
Electricity circuits Individual Appliance Circuits are dedicated to devices that draw enough current to warrant their own circuit.
Electricity circuits Appliance Voltage Garbage Disposer 120 Electric Range/Cooktop 240 Gas Range/Cooktop 120 Dishwasher 120 Electric Tankless Hot Water 240 Refrigerator 120 Microwave Oven 120 Exhaust Fan 120 Breaker Capacity Amps 20 50 20 20 30 20
Electricity circuits Ground Fault Circuit Interrupter Circuits are required for receptacles within 6 feet of a water source, such as a faucet or showerhead. Most receptacles mounted above a kitchen countertop or bath lavatory fall into that category.
Electricity Wiring Kitchen Wiring Dedicated circuit for the dishwasher Dedicated circuit for the disposer Dedicated circuit for the microwave (if built in) At least two 20 amp dedicated small appliance circuits for the outlets serving the countertops All outlets serving the countertop surface to be GFCI protected Dedicated range/cooktop/oven circuits Lighting Circuit
Electricity circuits Adding Circuits to the Breaker Panel Consult your electrician Replace breakers with wafer or mini breakers Add a branch panel piggybacked to main panel If it’s an old fuse panel replace it