1. ES Lesson 8: Capacitors What are capacitors? How are they used? How are they made? What are their sizes? What is an RC time constant? © 2012 C. Rightmyer, Licensed under The MIT OSI License, 20 July 2012

2. Peter van Musschenbroek’s “Leyden Jar” (an early version of a capacitor) Metal Ball

3. ES project 8-1. Make a capacitor http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html  demo 

4. Rolling our capacitor http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html

5. The finished capacitor http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html

6. What do capacitors used in electronic circuits look like? Here are some of them.

7. Capacitor come in a large range of sizes. 1 micro-Farad = 1  F = 10 ^-6 farad = (1/1,000,000) Farad 1 nano-Farad = 1 nF = 10 ^-9 farad = (1/1,000)  F 1 pico-Farad = 1 pF = 10 ^-12 farad = (1/1,000) nF

8. How capacitors work? Vs V c = 0 +Q = 0 -Q = 0 I c = 0 C = capacitance (farads) Q = charge on + plate (colombs) I c = dislacement current (amps) V c = voltage across capacitor (volts) Vs ++++++ - - - - - - - VcVc Electric Field +Q -Q electrons Vs ++++++ - - - - - - - VsVs Electric Field +Q -Q IcIc C = Q / V s Q = C V s I c = C dV c / dt V c = (1/ C) I c dt

9. ES ckt 8-2. Experiment with a capacitor + + 4700 uf  volts LED 220  Adapted from Discover Electronics: Mr Circuit One, Electronic Kourseware Interactive, 2002 (www.EKII.com)

10. Hookup diagram for ES ckt 8-2 push button switch + 4700 uf 220 LED + 9.0 volts  ckt 

11. Hookup diagram for ES ckt 8-3 (Same as ckt 8-2 except for the 1K resistor.) push button switch + 4700 uf 1K LED + 9.0 volts

12. ES demo 8-4. The “Blinking” Project  ckt 

13. ES demo 8-5. A variable tone oscillator +  volts 1 Meg  pot NPN 3904 B C E PNP 3906 B C E + 47  10  0.1  F  ckt 

14. What if we need a special size capacitor? How to calculate size if in series or parallel.

15. Backup slides

16. What is an RC time constant (  sec  ? After one time-constant (  ), the capacitor is ~ 63% discharged. After 5 time-constants (5  ), the capacitor is ~ 99% discharged. This chart can be used to help choose the size of capacitors and resistors that you will need for projects you will do if you take Beginning Electronics later on.

17. ES demo 8-4. Capacitor discharge after one time constant. + + 4700 uf VOM 9 volts

18. Hookup diagram for ES demo 8-4 push button switch + 4700 uf R + 9.0 volts :10 vdc Volt Meter  ckt 