* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download notes - Purdue Physics
Survey
Document related concepts
Nanofluidic circuitry wikipedia , lookup
Phase-locked loop wikipedia , lookup
Switched-mode power supply wikipedia , lookup
Operational amplifier wikipedia , lookup
Wien bridge oscillator wikipedia , lookup
Power electronics wikipedia , lookup
Power MOSFET wikipedia , lookup
Opto-isolator wikipedia , lookup
Resistive opto-isolator wikipedia , lookup
Current mirror wikipedia , lookup
Surge protector wikipedia , lookup
Electric battery wikipedia , lookup
Galvanometer wikipedia , lookup
Transcript
NOTES Ideal vs Real Battery • Ideal battery: no internal energy dissipation Energy conservation Work done by battery is equal to energy dissipated in resistor EMF ε = terminal voltage V • Real battery: internal energy dissipation exists dW > i2Rdt or ε > iR=V Resistors in Series The current through devices in series is always the same. i R1 R2 ε For multiple resistors in series: i i Req ε Real Battery = Resistors in Series The current through devices in series is always the same. i Req terminal voltage ε internal resistance For multiple resistors in series: Resistors in Parallel Devices in parallel has the same potential drop Generally, ••• DOCCAM 1 DEMO 5B-04 SUM OF VOLTAGE DROPS EQUALS EMF Kirchhoff’s Loop Rule Example When any closed loop is traversed completely in a circuit, the algebraic sum of the changes in potential is equal to zero. where is the potential difference across i-th device in the circuit: positive if potential rises negative if potential drops terminal voltage Loop Example with Two EMF Devices Ir1 IR1 IR2 ε2 ε1 Ir2 IR3 If ε1 <ε2, we have I<0 !? This just means the actual current flows reverse to the assumed direction. No problem! Finding Potential and Power in a Circuit But what is I? Must solve for I first! supplied by 12V battery The rest? Just means 0 V here into 4V battery (charging) dissipated by resistors Charging a Battery • Positive terminal to positive terminal • Charging EMF > EMF of charged device good battery (12V) Say, R+r1+r2=0.05Ω (R is for jumper cables). Then, battery being charged (11V) power into battery 2 • If connected backward, NO !! Large amount of gas produced Huge power dissipation in wires Using Kirchhoff’s Laws in Multiple Loop Circuits • Identify nodes and use Junction Rule: • Identify independent loops and use Loop Rule: Only two are independent. Same example (with parallel R combos) I1+I2 I2 • Sketch the diagram • Simplify using equivalent resistors I1 • Label currents with directions • Use Junction Rule in labeling • Choose independent loops • Use Loop Rule Replace by equivalent R=2Ω first. • Solve simultaneous linear equations NOTES Loop currents directly (with parallel R combos) I1 I2 I1 -I2 • Sketch the diagram • Simplify using equivalent resistors • Label loop currents with directions • Use Loop currents I1 and I2 • Choose interior clockwise loops . Set up cononical equations in Replace by equivalent R=2Ω first. . I1 I2 Ε format I1 (12 +6) +I2 (-6) = +18 (Emf) Left loop I1 (-6) + I2 (6+3+2) =+21 (Emf) Right loop Note Symmetry of 2 Equations in 2 unknowns Kirchoff Circuit Analysis Tips (Loop current system easier) • Sketch the diagram • Simplify using equivalent resistors • Label currents with directions • Use Junction Rule in labeling • Choose independent loops • Use Loop Rule • Solve simultaneous linear equations (Loop current system easier !!) DOCCAM 1 DEMO 5B03 MULTIMETERS AND VOLTAGE PARADOX Basic Ammeter and Voltmeter Ammeter: an instrument used to measure currents • It must be connected in series. • The internal resistance of an ammeter must be kept as small as possible. Voltmeter: an instrument used to measure potential differences • It must be connected in parallel. • The internal resistance of a voltmeter must be made as large as possible. Galvanometer Inside Ammeter and Voltmeter Galvanometer: a device that detects small currents and indicates its magnitude. Its own resistance Rg is small for not disturbing what is being measured. galvanometer Ammeter: an instrument used to measure currents shunt resistor Voltmeter: an instrument used to measure potential differences galvanometer NOTES PHYS 241 – Extra Quiz 3 What is the magnitude of the current through R2 ? a. 0.33A b. 2.5A c. 0.75A d. 1.5A e. 0.5A 10Ω 10Ω 15V R1 R3 10Ω R2 15V PHYS 241 – Extra Quiz 3 What is the current through R3 ? a. 0.375A b. 0.5A c. 0.75A d. 1A e. 1.5A 20Ω 20Ω 30V R1 R3 20Ω R2 30V