Physics 19: 5-8 RC Circuits
Text Reading: Giancoli, Physics - Principles with Applications, Chapter 19: Sections 5 to 8
- 19.5 Capacitance in parallel and series circuits adds up exactly the reverse of resistance. In a series of two capacitors, you add 1/C1 + 1/C2 = 1/Ctotal. In a parallel circuit, you simply add capacitances: C1 + C2 = Ctotal.
- 19.6 The voltage of an RC circuit follows the rule V across the capacitor = emf * (1 - e-t/RC) where e is the base for natural logarithms. This type of circuit has to be analyzed using calculus (and in fact, can be set up to be analogous to many differential equations). The value t = RC is the time it takes to charge a capacitor to 63% of its maximum.
- 19.7 Electrical shocks can burn tissue or disrupt the normal electrical impulses used to trigger heartbeat or brain functions. Always follow safe practices in working with electrical circuits.
- 19.8 Ammeters measure current, voltmeters measure potential difference, multimeters measure both, and ohmmeters measure resistance.
- Capacitance in a Series Circuit:
- Capacitance in a Parallel Circuit:
Read the following weblecture before chat: DC Circuits: Capacitance and Resistance
Use the capacitance lab to experiment with plate charges.'
- What happens to the capacitance and the electric field if you vary the voltage on the battery?
- What happens if you vary the plate separation?
- What happens if you vary the plate area?
Physics simulation Java Applets are the product of the PHET Interactive Simulations project at the University of Colorado, Boulder.
Please return to the Learn Physics Today! site, to look at the Unit 3, chapter 15 lecture on the more exotic aspects of circuits.
Chat Preparation Activities
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