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Physics 111 – BSC Lecture 1 Page 1 of 9 Jim Siegrist Phone: 486-4397 Email: [email protected] Room (at LBL): 50-4055 Room (Campus): 309 Old Leconte Administrative Issues Lectures Reserve T & Th 5-6 PM (location) Only about 12 lectures for the semester, mostly they will be on Thursdays. --- Must watch for lecture dates. --- Current Plan, next 3 lectures: Today lec 1 Thur Jan 18 lec 2 Tues Jan 23 lec 3 Thurs Jan 25 lec 4 Tues Jan 30 Course Grades 1. Must hand in all labs to pass, including P/F labs. 2. See yellow sheet for grade breakdown. Grading: Full Write-Ups: Introduction 10 points Conclusion 10 points + 3 or 4 random questions x 15 points Prelab Questions 20 points = 100 points Will not grade all the problems all the time (up to TAs) Supplemental Problems +2 points each -2 points per question with no answer –3 points per day late Work will not be accepted after the solutions have been posted. P/F Labs: +50 points if you attempt all the questions –2 points per question with no answer –3 points per day late Final Projects MUST be in on time. Send me an email if you don’t want your paper posted. Course Content • Goal of this course is to teach the basics of modern electronics. You’ll need this for the next semester of Advanced Lab. We assume you know electricity and magnetism at the level ofPhysics 111 – BSC Lecture 1 Page 2 of 9 Physics 7 and take you to the point that you can design your own circuits by the end of the semester. • Main elements that we’ll learn about in lecture: - Concepts - Instruments & Devices - Measuring Techniques - Circuit Analysis Techniques - Tools • Topics in lectures tend to jump around among these – I’ll try to note which area I am talking about as I change topics. • I’ll also give advice and information at the start of each lecture – the most important stuff will be in the front of the notes, so I hope you don’t miss it. Notes will be posted to the web after lecture. Advice for the course: * Reading material for each lab at front of each handout. * Labs are quite long, so come in early. * This course is harder than you think – give it plenty of time. * Find a partner, sign up for 2 afternoons/week (yellow form) * Course grade strongly correlated with lecture attendance; will work some problems in lecture * Some labs P/F – see handout. No introduction or conclusion write-up needed for P/F labs. * Office Hours: by appointment * Schedule of write-up due dates in handout. * All write-ups must be NEAT. * Example write-up in handout is minimum acceptance for P/F labs – really need diagrams and descriptions. * Label axes on plots. * Indicate units. *** Note hand symbol for TA signoff – get before proceeding. Advice this week: Scope manuals in lab if needed – triggering, x-y mode DMM description in notes – read it! Read this & next week’s lab – I’ll talk about next week on Thursday. Motivation – Why is the course goal important? Physics is Experimental Science ⇒ What we know about nature determined by what we can measure. Experiment crucial to guide theoretical development – witness development of Quantum Mechanics in 20’s Standard Model in 70’s What limits experiment? – Instrumentation! (brains) Why is electronics important in this?Physics 111 – BSC Lecture 1 Page 3 of 9 1. Huge technology base (industry) around electronics ⇒ opportunity to exploit for new science. 2. ~ All modern instruments depend crucially on electronics for read out (and data handling!). 3. Many electronic devices operate at or near the theoretical limit allowed by quantum mechanics or thermodynamics. [e.g. position & momentum, noise in amplifiers] 4. Beating limits of measurement therefore is a major industry for physical science – other limits cost, size, sensitivity, etc. exist and also have to be beat. 5. Therefore you need to know this to be a physicist (theory or experimental) Concepts I. Circuits Definitions – Units Charge electron charge is –1.6x10–19 Coulombs Current I1 Æ flows in arbitrary reference direction I1 is positive if positive charges move in the reference direction, else negative Charge dQ moves past a point in time dt ⇒ current dtdQ in ondsCoulombsAmperesec≡ Voltage QxEnergyPotentialElectricalxV)()( = – Unit = Volts Zero is arbitrary! Zero = reference point ⇒ common Only Differences Matter Power Charge +Q moves from V1 to V2 ⇒ a charge in energy of Q(V2 – V1) Joules For a steady state current I, P = I(V1 – V2) ≡ IV = Joules/sec ≡ Watt ≡ Amp • Volt Circuits imply a closed loop. In the lab, be sure you have made complete circuits. Equivalent Circuits, Kirchoff’s LawsPhysics 111 – BSC Lecture 1 Page 4 of 9 1234ABCD Definitions: Wire from C – B has no resistance (ideal wire) ⇒ VC = VB Node: point at which 2 or more circuit elements are connected Branch: two-terminal circuit element connected between nodes (ABOVE: 3 nodes, 4 branches) Nodes are NOT separated by wires. Kirchoff’s Current Law: no charge accumulates on a wire ⇒ [sum of all currents entering a node is zero] (charge conservation) Kirchoff’s Voltage Law: sum of all voltage drops around a complete loop is zero (potential at any instant is well defined) (⇒ physical size of circuit is much less than λ at frequency in question) Circuit Elements & Symbols R or acb abacRR ≤≤0 ; Ohms, V = IR C variableversion CVQdtdVCIFaradsCdtICQV==⇒∫== NOTE: Stored energy 221CVU = so be careful – big capacitor can give you a nasty shock. L HenriesdtdILV = • Real signals come from transducers, e.g. phototube, photodiode, radiation detector, etc. • Learn more about these mostly next semesterPhysics 111 – BSC Lecture 1 Page 5 of 9 • Here, consider ‘ideal’ sources DC Voltage Source +–Vo ‘ideal’ ⇒ V independent of I AC Voltage Source vo vo = Vo sin ωt or Vo cos ωt lowercase, usually Current Source RL‘ideal’ ⇒ I independent of load resistor RL ‘compliance’ – limit source can provide * Useful to review microscopic definition of resistance – Berkeley Series, Vol. II, Sec. 4.3 – 4.7 Component Specs • Resistors – 81,41,21 Watt – carbon composition in lab Color Code Tolerances Resistance varies with T, V, time, humidity, etc. Power = IV = I2R


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