Physics Class Notes: Topics Covered in Week 12 - Resistors and Capacitors, Assignments of Physics

Download Physics Class Notes: Topics Covered in Week 12 - Resistors and Capacitors and more Assignments Physics in PDF only on Docsity! Phys. 122-02: Monday, 06 October • HW 5: due today by noon. • HW 6: chapter 25, problems 22, 50, 56, and 59, and chapter 26, problems 17 and 22. • Mastering Physics: Fourth assignment due Tuesday. Fifth assignment due a week later. • Reading: Chapter 26, sections 1 through 3, for Wednesday. Example: Find the equivalent resistance of each network. Clickers: For a capacitor in a circuit, what does the power represent in P = I ΔV ? • a) Energy per time being stored in the capacitor • b) Energy per time being released from it • c) It depends upon the relative direction of I to the direction in which ΔV is positive • d) The power is being used by resistors in the same circuit • e) The power gained by each electron Why ever use the BIG battery, if the small one can provide the same ΔV? The answer is internal resistance: the larger battery has less, and so it can provide more current at the same voltage. Rule for resistors: The voltage drops in the direction of current flow! However, a charging battery has the current flowing in the opposite direction, and its terminal voltage will be larger than the open-circuit (no current) value! The fluid (water) analogy... updated Electrical Thing  Charge  Voltage  Electric Field  Capacitor  Current (in a wire)  Resistor  Battery (source of EMF) Fluid thing  Fluid (water)  Pressure  Pressure difference  Water tank  Current (in a pipe)  Pipe filled with sand  Pump (can make the fluid flow “uphill”) A very simple series network R ~ Current from R, I can't go anywhere but through R,... gE “+... so current through R, and R, is the same. Copyright © 2007 Pearson Edveation, ishing as Pearson Addison-Wesley.  Kirchhoff's Loop Rule: The sum of voltage drops around any closed loop must be zero. Node A Current into node A is 0: Ve -,+1,+1h,=9 g Voltage charges around loops sum to 0: R, loop 1 Ej = TR, = IR, —= 0 loop 2: E> a IR, = I,R, =0 Node B Copyright © 2007 Pearson Education, Inc., publishing as Pearson Addison-Wesley. Strategy: set up unknown currents (with any signs). Apply Kirchhoff's rules to independent current junctions and voltage loops. Finally, solve the (5) equations (for 5 unknowns). Example: A resistor and capacitor together