building services cspa lecture 5

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