Previous Stuffmore dc circuitsWhich diagram ain’t right?Which bulbs in the diagram will light?Slide 5Which bulb do you think is brighter?Slide 7ResistanceMeasuring VoltageMeasure currentSlide 11Which lamp is brighter?Where is the current largest?Slide 14Slide 15Slide 16Slide 17which has more current?Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Resistance increases with length.Slide 27Slide 28Resistance inverse to area.Resistivity W-mSlide 31What is the resistance A-b?Slide 33Previous StufFebruary 15, 2010more dc circuitsWhich diagram ain’t right?A B CWhich bulbs in the diagram will light?A. All lights will light.B. A and B will lightC. A and C will lightD. B and C will lightE. None of these answers are correct.AB CIt is the same diagram that is on the handout.A steady current flows through the wire shown below.At one point, the wire suddenly narrows. Which of thefollowing is correct?IA BA I(A)=I(B)B I(A)<I(B)C I(A)>I(B)D None of the aboveWhich bulb do you think is brighter?A. AB. BC. CD. All the sameABCA current I flows through a device. The difference in potentialfrom one side of the device to the other is V. How much POWERis dissipated in the device?:(current) x (Potential Difference)Usually written as P=IVNoteQItE Q V QP V I Vt t tPD=DD D D D= = = D = DD D D=February 17, 20102/17/2010Resistivity8ResistanceMeasuring Voltage2/17/2010Resistivity9Set to proper scaleMeasure current2/17/2010Resistivity10Set to proper scale2/17/2010Resistivity11But First … a few clicksWhich lamp is brighter?AA. R1 on the leftB. R2 on the rightC. Both the sameWhere is the current largest?2/17/2010Resistivity13ABCA Point AB Point BC Point CD They are all the same2/17/2010Resistivity142/17/2010Resistivity15Which bulb is brighter? A. R1 on the topB. R2 on the bottomC. Both the sameThe two batteries and all of the resistors (light bulbs) have the same values. Which light bulb is brighter?BBABA Bulb A is BrighterB Bulb B is brighterC Both are the samewhich has more current?2/17/2010Resistivity18ABC They are the same.Normal Wire High Resistance Wire (W)which has more current?2/17/2010Resistivity19ABC They are the same.Normal Wire High Resistance Wire (W)which has more current?2/17/2010Resistivity20ABC They are the same.Normal Wire High Resistance Wire (W)2/17/2010Resistivity21February 17, 20102/17/2010Resistivity22Resistance2/17/2010Resistivity232/17/2010Resistivity24which has more current?2/17/2010Resistivity25ABC They are the same.Normal Wire High Resistance Wire (W)Resistance increases with length.2/17/2010Resistivity26R L�which has more current?2/17/2010Resistivity27ABC They are the same.Normal Wire High Resistance Wire (W)which has more current?2/17/2010Resistivity28ABC They are the same.Normal Wire High Resistance Wire (W)Resistance inverse to area.2/17/2010Resistivity29 is resistivity units=-m1 =conductivityis a property of the materialLRAr=Resistivity -m2/17/2010Resistivity302/17/2010Resistivity31A wire has a resistance of R Ω. It is melted down, and from the same volume of metal a new wire is made that is two times longer than the original wire. What is the resistance of the new wire?Idea: What stays the same??VOLUME!(2 )( )22 44( / 2)newnewnewLRAV LA L AAAL LR RA Arr r== === = =What is the resistance A-b?2/17/2010Resistivity322/17/2010Resistivity33That’s why you pay tuition .. isn’t
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