building services cspa lecture 5
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TRANSCRIPT
Unit - 3
BUILDING SERVICES – I
Lecture - 5
Electricity: Basic Concepts and Terminology
Source of electricity, generation to end user connection, service connections
•Electricity by definition is electric current that is used as a
power source
What Is Electricity ?
•This electric current is generated in a power plant, and then
sent out over a power grid to your homes, and ultimately to
your power outlets.•The movement of charges
such as electrons is called
current, and this electrical
current is what powers
household appliances.
Electric Current =
Charge PassingThrough A Given Area
------------------------------- Time
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
Generating Electricity
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. hydroelectric generation
Turbine: a fan-like device
which turns in response
to the pressure of falling
water
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. hydroelectric generation
Generator: a coil of wire
turned inside a magnet
generates electricity
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. hydroelectric generation
Power lines: electricity
generated is carried in
wires over long distances
to our homes
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. tidal generation-high & low tides occur twice daily
-tidal water movement can be used to turn aturbine
Generating Electricity
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. thermal generation-water is heated to make steam-pressure builds & the steam can only escape by passing through a turbine-this turns the turbine
Generating Electricity
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. thermal generationFossil Fuel: burning coal, oil, or natural gas
can be used to heat the water
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. thermal generationFossil Fuel: burning coal, oil, or natural gas
can be used to heat the waterRadioactive Material: when the nuclei of
uranium atoms break apart huge amounts of energy is released, which can be used to heat the water
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. thermal generationFossil Fuel: burning coal, oil, or natural gas
can be used to heat the waterRadioactive Material: when the nuclei of
uranium atoms break apart huge amounts of energy is released, which can be used to heat the water
Biomass: biodegradable wastes can be burned to heat the water
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. Wind-the blades themselves act as a turbine to turn the middle of the generator to produce
electricitycalled wind turbines, not wind mills
Generating Electricity
Electricity Generation: electrical energy has to be made by conversion from some other form of energy
e.g. Lightphotovoltaic cells: converts light directly into electrical energy
Generating Electricity
World Electricity Generation
• Electricity is supplied through “hot wires”, comparable to
pressured water supply pipes. • At points along the wires are lighting outlets, switches, and
receptacles. Turning on a light switch or plugging equipment into a receptacle is comparable to opening a faucet/valve.
Electrical Supply
Electrical supply
Can be compared to
Water supply
Voltage
Equivalent to water pressure; pump controls water pressure; generator or battery controls voltage; standard voltage is 120/240; most common low voltage is 12V
voltage
water pressure
Can be compared to
Amperage
Electrical current; equivalent to flow of water (gal/sec)
Resistance: Opposition to flow of current; amount of resistance is affected by:
•Material•Diameter •Length
Conductors
Wire over which electrons are transmitted
Increase in wire number = decrease in size
Copper Wire: Relation between Diameters and
Amperage and Resistance
Insulators
Holds electrical current in proper path, similar to a hose
Wattage
Unit of power; rate at which a device converts current to another form (heat or motor)
(Voltage x Amperage)
Watthour: Unit of energy; measures amount of energy/electricity used in one hour
Watts x hours of use=watthours or KWHR, e.g.,
100 w x 24hrs = 2400 whrs/day = 2.4 KWHRs
2.4 KWHR/day x 30 days/mo. = 72.4 KWHR/mo
Direct CurrentDirect current: Current flows in one direction
Alternating Current
Alternating current: Current flows in single direction but reverses direction at regular intervals
Other terms
Series circuit: If one lamp fails, remaining lamps go out
Parallel circuit: If one lamp fails, others remain lighted
Open circuit: Circuit is brokenClosed circuit: Circuit is completeShort circuit: If there is a fault, electricity
will take path of least resistance to reach ground
Short circuit