Slide 1What’s UpOur Meter - OHMSThe (*#&) MultimeterThe Issues??The ScalesThe MeasurementsR bulb Not a ConstantThe Numbers (T in 0K)Our wall provides ACAveragesWhat is the average POWER?RMS VoltageSlide 14EXAM2Examination #2Wednesday, March 16th.What’s UpThis weekMore on DC circuits including Kirchoff’s LawsQuiz on FridayCurrent thought on next exam:Wednesday, March 16thAll material will be covered up to the previous Monday. All of the current chapter will be concluded. We may have some material on magnetism if we are sufficiently lucky.Problem Solving SessionsNobody seems interested but we will do a session this Friday at 12:30 (In Physical Science Building) if there is interest. Tell me!The equivalent can be obtained during office hours .. larger groups can be accommodated in the small conference room at the end of my hallway.Our Meter - OHMSTemperature SensorThe (*#&) MultimeterConnectionsDisplaySelectorScaleThe Issues??Bulb has specifications ofV=2VI=60msFrom this: R=V/I=2/0.06=~33 ohms.These numbers vary from bulb to bulb.The ScalesThe numbers you posted are full-scale readings for each range. For example, if you get a reading of 3.87 with the scale set to 20K, then the resistance is 3.87K ohms. If you had the same reading with the scale set to, say, 2M, then the resistance is 387K ohms.The reason they use a "2" is to use what is known as a half of a digit. In other words, a typical 8-segment display can show all 10 digits, whereas a 1 can be displayed with a vertical line (the 'half digit'). So the max readout is actually 199. (with a 2-1/2 digit readout)The Measurements2KW Scale0.004 W200 W Scale4.0WBattery ~1.5V I= v/R = 1.5/4.0 = 0.4 AMPSWhat’s going on here??R bulb Not a ConstantLinear ApproximationThe Numbers (T in 0K)4(1 0.0045 2300) 45R = + � � WMystery Solved!Note: A light bulb operates at about 2700 0KOur wall provides ACAveragesAverage Voltage is ZEROWhat is the average POWER?222 2012???VVP I R Sin ftR R RPp= = = ==2 22 22 2222sin cos 1sin cos 1sin cos2 sin 11sin21sin2x xx xx xxxx rms+ =< >+< >=< >=< >< >=< >=< >= =RMS Voltage222 2022 220 0 0121 1222VVP I R Sin ftR R RV V VP Sin fR R Rpp= = = =� �< >= < >= =� �� �Root Mean Square (rms) voltageThe rms Voltage Delivered toyour home is 120 VoltsWAKE UP!!Get back to Unit -
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