《Fundamentals of Physics精品教学-华南理工》25 Capacitance.pptVIP

Fundamentals of Physics 25 Capacitance 25-1 The Uses of Capacitors An electrical device to store electric charge, energy, and information Have many usages in electronic and microelectronic devices? Parallel-plate capacitor 25-2 Capacitance The basic structure of capacitor: two plates Fundamentals of Physics 25 Capacitance The ability of a capacitor to store charge Capacitance of a capacitor; depend only geometry Fundamentals of Physics 25 Capacitance 25-2 Capacitance Fundamentals of Physics 25 Capacitance 25-2 Capacitance Charging a capacitor 25-3 Calculating the Capacitance 1. Assume q on the plates 2. Calculate E between the two plates in terms of q Fundamentals of Physics 25 Capacitance 3. Knowing E, calculate V 4. Calculate C A parallel-plate capacitor The physical meaning of this result Fundamentals of Physics 25 Capacitance 25-3 Calculating the Capacitance A cylindrical capacitor Fundamentals of Physics 25 Capacitance 25-3 Calculating the Capacitance A spherical capacitor Fundamentals of Physics 25 Capacitance 25-3 Calculating the Capacitance An isolated sphere Fundamentals of Physics 25 Capacitance 25-3 Calculating the Capacitance R Fundamentals of Physics 25 Capacitance 25-4 Capacitors in Parallel and in Series Capacitors in Parallel: Directly wired together at one plate and together at the other (1) Have same V; (2) Total charge equals the sum Equivalent capacitor Fundamentals of Physics 25 Capacitance 25-4 Capacitors in Parallel and in Series Capacitors in Series: wired serially, one after the other (1) Total potential equals the sum; (2) Have identical charges Fundamentals of Physics Sample Problem (a) Find the equivalent capacitor for the combination of capacitors shown in the figure. Assume C1=12 μF, C2=5.3 μF, C3=4.5 μF. Fundamentals of Physics Sample Problem Fundamentals of Physics Sample Problem (b) Potential difference is V=12.5 V. What is the charge on C1? Capacitor 1, with C1=3.55 μF, is ch