LECTURE 16 Hand Hand in in your your homework homework after after class: class: Print Print both both •• your your name name •• your your TA’s TA’s name name on on your your assignment, assignment, and and place place itit in in the the appropriate appropriate box box DEMO: all bulbs are identical 4 1 3 E 2 5 6 Prediction Prediction#1: #1:Bulbs Bulbs11&&22 are areconnected connectedfirst. first.IfIf bulb bulb33isisconnected connectednext, next,then then 1.) bulb 3 will be brighter than 1.) bulb 3 will be brighter than11oror22but butnot not1+2 1+2 2.) 2.)bulb bulb33will willbe bebrighter brighterthan than1+2 1+2 3.) 3.)bulb bulb33will willbe beasasdimmer dimmerthan thaneither either11oror22 Prediction Prediction#2: #2:Bulbs Bulbs44&&55 are areconnected connectedfirst. first.IfIf 66isisconnected connectednext, next, 1.) 1.)bulb bulb44will willbe bebrighter brighterthan thanbefore before 2.) bulb 4 will be dimmer than before 2.) bulb 4 will be dimmer than before 3.) 3.)bulb bulb44will willbe bethe thesame sameasasbefore before Prediction Prediction#3: #3:All Allbulbs bulbsare areconnected. connected.The Thebrightest brightestbulb bulbisis 1.) 1.)Bulb Bulb#1 #1 2.) bulb #2 2.) bulb #2 3.) 3.)bulb bulb#3 #3 4.) bulb #4 4.) bulb #4 5.) 5.)bulb bulb#5 #5 6.) 6.)bulb bulb#6 #6 Concept Concept Test: Test: An Anammeter ammeterAAisisconnected connected between betweenpoints pointsaaand andbbin inthe thecircuit circuitbelow, below, in inwhich whichthe thefour fourresistors resistorsare areidentical. identical. The Thecurrent currentii through throughthe theammeter ammeterisis i 1.1.I/2. I/2. 2.2.I/4. I/4. 3.3.zero. zero. 4.4.need needmore moreinformation information Exercise: Exercise: Twelve Twelve identical identical resistors, resistors, each each of of resistance resistance R, R, are are connected connected as as edges edges of of aa cube, cube, as as shown shown in in the the figure. figure. What What is is the the equivalent equivalent resistance resistance between between two two diagonally diagonally opposite opposite nodes nodes (say, (say, aa and and d) d) ?? RC circuits • Circuit containing a resistance R and a capacitor C + - E Question:Can such a circuit sustain a constant current ? 1. Yes 2. No 3. Depends on values of C and R Concept Concept Test: Test: In Inthe thecircuit circuitshown shownbelow, below, the thecapacitor capacitorisischarged chargedto toaapotential potentialdifference difference VV00..The Theswitch switchisisinitially initiallyopen, open,but butthen thenthrown thrown closed. closed.Immediately Immediatelyafter afterthe theswitch switchisisclosed, closed, the thecurrent currentin inthe thecircuit circuitisis 1.1. 2.2. 3.3. VV00/R /R zero zero need needmore moreinfo info Concept Concept Test: Test: The Thecapacitor capacitorin inthe thecircuit circuit below belowisisinitially initiallyuncharged. uncharged.Immediately Immediatelyafter after the theswitch switchisisclosed, closed, a.) a.)the thecurrent currentisis isis 1.1. 2.2. 3.3. E/R E/R zero zero need needmore moreinfo info b.) b.)VVacross acrossthe thecapacitor capacitor 1.1.EE 2.2.zero zero 3.3.need needmore moreinfo info Demonstration Part I S1 R1 E S2 R2 C When the switch S1 is closed, the intensity of the bulb R1 1. is initially high and then gradually drops 2. gradually increases then drops to zero 3. remains zero (does not shine) Demo: Part II S1 R1 E S2 R2 C S1 is closed, and then opened again. If S2 is now closed, the intensity of the bulb R2 1. is initially high and then gradually drops 2. gradually increases then drops to zero 3. remains zero. What happens to bulb R1? 1. is initially high and then gradually drops 2. gradually increases then drops to zero 3. does not shine S1 S2 R E R C Switch S2 is kept closed. What is the current through the battery a.) immediately after closing the switch b.) steady state current c.) what is the maximum voltage across C?