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Unformatted text preview: 2/15/2012 1 Lecture 11-1 2/15/2012 1 ANNOUNCEMENT NOTE THAT FEW EQUATIONS WILL BE GIVEN – YOU ARE REMINDED THAT IT IS YOUR RESPONSIBILITY TO CREATE WHATEVER TWO-SIDED CRIB SHEET YOU WANT TO BRING TO THIS EXAM. *Exam 1 : Monday February 20, 2012, 8 PM - 10 PM * Location: Elliot Hall of Music *Covers all readings, lectures, homework from Chapters 21 through 24. *The exam will be multiple choice (15-17 questions). Be sure to bring your student ID card and your own one-page (two-side) crib sheet. The equation sheet that will be given with the exam is posted on the course homepage. Click on the link on the left labeled “EquationSheet” Lecture 11-2 Chapter 25 Electric Current and Direct-Current Circuits • 25-4 Combinations of Resistors • 25-5 Kirchoff’s Rule Lecture 11-3 3 Energy and Power in Electric Circuits (Review) • Using Ohm’s Law we can write equivalent formulations of the power • The unit of power is the watt (W) • Electrical devices are rated by the amount of power they consume in watts • Electricity bill is based on how many kilowatt-hours of electrical energy you consume 2 2 V P iV i R R = = = with kW h = power times time 1 kW h = 1000 W X 3600 s = 3.6 x 10 6 joules Lecture 11-4 emf – Electromotive Force • An emf device is a charge pump that can maintain a potential difference across two terminals by doing work on the charges when necessary. Examples: battery, fuel cell, electric generator, solar cell, thermopile, … • Converts energy (chemical, mechanical, solar, thermal, …) into electrical energy . h Within the emf device, positive charges are lifted from lower to higher potential. h If work dW is required to lift charge dq , [ ] dW Volt dq dq dW ε ε ε = = = ⇒ emf 2/15/2012 2 Lecture 11-5 EMF Devices - Directions • An emf device (e.g., a battery) keeps the positive terminal (labeled +) at a higher electrical potential than the negative terminal (labeled -) • When a battery is connected in a circuit, its internal chemistry causes a net current inside the battery : positive charge carriers move from the negative to...
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This note was uploaded on 02/21/2012 for the course PHY 241 taught by Professor Virgil.e.barnes during the Spring '11 term at Purdue.
- Spring '11