Activity 6.2.3 Resistance



Activity 6.2.3 ResistanceIntroductionResistance to current flow in a circuit can be good or bad. Even the best conductors provide some resistance. Electric power lines travel long distances on very good conductors, but engineers try to improve systems to lose as little energy as possible. Resistance is good, though, if it is protecting an electronic component. If you build a circuit and a component gets very hot, then that is a sign that it should have been better protected with additional resistance. Resistance can also control devices. Increasing resistance on a speaker turns the volume down.EquipmentSchematic Symbols ChartEngineering notebookMultimeterSnap Circuits? componentsBoard, voltage source, and power supplyRed LEDVariable resistorsVarious sizes of snap wiresProcedureComplete the questions below as your teacher shows the Resistance presentation.All resistors ___________ or _____________ the flow of electrons.As resistance __________________ current _______________________In electrical circuits there are three factors which affect the amount of resistance. They are:Resistance is measured in __________ The abbreviation is _____.__________ ohms = __________ resistance = __________ currentThe basic materials in most fixed resistors are ________ and _________.Color bands 1 – 2 determine ____________________. Color band 3 is the______________. Color band 4 determines ___________ or__________.Prefixes are used to eliminate __________. The prefix Kilo means __________. The abbreviation for Kilo is ____.The prefix Mega means __________. The abbreviation for Mega is ____.1 – 999 Ω How? 1000 – 999,999 Ω How? 1,000,000 Ω and up How? Complete the Schematic Symbols Chart as you learn about different electronic components and functions.Accuracy CalculationConverted resistance x Tolerance % = Calculated ToleranceFor our class, our tolerance will always be 5% soCalculated Tolerance = Converted Resistance x 0.05Accuracy Range is reported as: Calculated resistance ± calculated accuracyBe sure to use the same units in both resistance and accuracy.Examples:ColorBand 1ColorBand 2ColorBand 3Calculated ResistanceConverted ResistanceTolerance(± 5%)AccuracyRange??????±High?Low??????±High?Low??????±High?LowRead the color bands on the supplied resistors, and, using the chart on the following page, calculate the resistance, the converted resistance.Have your instructor check your work before you calculate tolerance amount and range.Measure the amount of resistance in each resistor using the multimeterMeter SettingsRange measures up to….Label2002K20K200 K2MIf the meter reading falls within the accuracy range, the resistor rating is “good.” If the meter reading falls outside the accuracy range, the resistor rating is “bad.”Remember:Current will always follow Band 1Band 2Band 3Calculated ResistanceConverted ResistanceTolerance Amount(± 5%)Accuracy RangeMetered ResistanceRating??????±?High??Low??????±?High??Low??????±?High??Low??????±?High??Low??????±?High??Low??????±?High??Low??????±?High??LowConclusionDescribe a system that would be dangerous if resistance were not a part of the circuit.Why are fixed resistors’ values indicated by color bands rather than printing the numeric value on their exterior?Use colored pencils to color the bands on the resistors below to identify the appropriate resistance values.300 Ω47 Ω21 KΩ9.8 KΩ560 KΩ ................
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