ELECTRICAL AND MECHANICAL SYSTEMS IN BUILDINGS

CURRENT , ELECTRIC POTENTIAL and RESISTANCEELECTRICITY - the flow of electron from atom to atom in a conductor- constitutes a form of energy which occurs naturally only in unusable forms such as lightning and other static discharges- unlike fuels and heat, it cannot be stored and therefore must be generated and utilized at the same instantCURRENT (Ampere) - is the flow of charged particles through a conducting mediumConductor material or object that allows electricity or heat to move through it-when electricity flows in a conductor, a certain number of electrons pass a given point in the conductor in 1 second.- AMPERE unit of measure for the flow of current in a circuitELECTRIC POTENTIAL (Volt) -electrical pressure- the stored energy when there is charge differential between two points.- when there is Voltage differential or Electrical Potential between two points in a conductive material, charged particles will be forced to move.- force attraction , or tendency to flow , between the electrified particles concentrated at the positive and negative terminals- VOLT unit of measure for Electric potential

RESISTANCE (Ohm) - a material's opposition to the flow ofelectriccurrent - measure of materials difficulty in allowing electrical conductionOHM unit of measure for Electric ResistanceInsulator materials that resist the flow of currentCONDUCTANCE (Siemens)- measure of a materials ease in allowing movement of charged particlesANALOGY

OHMS LAW -Voltage pushes Amperage through ResistorsThe current (I) that will flow in a direct current circuit is directly proportional to the voltage (V) and inversely proportional to the resistance ( R) of the circuit. Expressed as an equation, the basic form of Ohms law states that : I = V / RSAMPLE PROBLEMS:Problem:An incandescent lamp having a hot resistance of 66 ohms is put into a socket that is connected to a 115 V supply. What Current flows through the lamp?Solution:Given:R = 66 ohmsV= 115 VI = ? Formula:I = V / R I = 115 V / 66 OhmsI = 1.74 Amperes

Problem:a bathroom heater draws 11 Amperes at 120 V. What is the hot resistance?Solution:Given:I = 11 AmperesV= 120 VR= ? Formula:R = V / IR = 120V / 11 AmperesR = 10.91 OhmsProblem:A household electric water heater is rated 220 V and 20 Amperes. What is the units resistance when drawing this amount of current? Solution: Given:I = 20 AmperesV= 220 VR= ? Formula:R = V / IR = 120V / 11 AmperesR = 10.91 Ohms

ELECTRIC CIRCUIT- a complete conducting path that carries current from a source of electricity to and through some electrical device (or load) and back to the source.- a current can never flow unless there is complete (closed ) circuit.CIRCUIT ARRANGEMENTSSERIES CIRCUITS- The elements are connected one after the other in series. Thus, the resistance and voltages add.- A practical application of series circuit is found in an incandescent lamp street lighting circuits where the loss of one lamp can disable the entire circuit.- In any series circuit, the total Resistance (R) is the sum of resistance around the circuit.

Thus,

Total Resistance = R1 + R2 + R3

PARALLEL CIRCUITS- when two or more branches or loads in a circuit are connected between the same two points- Multiple loads are across the same voltage and, in effect, constitute separate circuits.therefore, in the circuit is the sum of the individual currents flowing in the branches.- Loads connected in parallel are equivalent to separate circuits superimposed into a single connection. Each load acts as an independent circuit unrelated to, and unaffected by the other circuits.

Thus, Total Current IT = I1 + I2 + I3

ELECTRICAL SYSTEM IN BUILDINGSELECTRICAL POWER SYSTEMa network of electrical components used to supply, transmit and use electric power.COMPONENTSUTILITY transmitted power from the power plantTRANSFORMER devices that changes or transforms alternating current of one voltage to alternating current of another voltage.STEP UP a transformer rated 120/480 v transforms lower volt, 120 ac to 480 ac bigger loadSTEP DOWN to transform a bigger load to lower voltageMETER - keeps a record of power consumptionDISTRIBUTION PANELS BRANCH CIRCUITS ELECTRICAL DEVICES -

POWER DISTRIBUTION IN SMALL BUILDINGS

POWER DISTRIBUTION IN LARGE BUILDINGS

CIRCUIT BRANCH (LIGHTING) CIRCUIT BRANCHSOURCETRANSFORMERSERVICEMETERPANELCONVENIENCE OUTLETLIGHTING FIXTURE

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