ES Lesson 8: Capacitors What are capacitors? How are they used? How are they made? What are their...
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Transcript of ES Lesson 8: Capacitors What are capacitors? How are they used? How are they made? What are their...
![Page 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,](https://reader035.fdocuments.us/reader035/viewer/2022062315/56649d6f5503460f94a5168c/html5/thumbnails/1.jpg)
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
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Peter van Musschenbroek’s “Leyden Jar”(an early version of a capacitor)
Metal Ball
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ES project 8-1. Make a capacitor
http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html
demo
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Rolling our capacitor
http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html
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The finished capacitor
http://sci-toys.com/scitoys/scitoys/radio/homemade_radio.html
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What do capacitors used in electronic circuits look like? Here are some of them.
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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
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How capacitors work?
VsVc = 0
+Q = 0
-Q = 0
Ic = 0
C = capacitance (farads)
Q = charge on + plate (colombs)
Ic = dislacement current (amps)
Vc = voltage across capacitor (volts)
Vs++++++
- - - - - - -
VcElectric Field
+Q
-Q
electrons
Vs++++++
- - - - - - -
VsElectric Field
+Q
-Q
Ic
C = Q / Vs
Q = C VsIc = C dVc / dt
Vc = (1/ C) Ic dt
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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)
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Hookup diagram for ES ckt 8-2
push button switch
+
4700 uf
220
LED
+
9.0
volts
ckt
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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
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ES demo 8-4. The “Blinking” Projectckt
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ES demo 8-5. A variable tone oscillator
+
volts
1 Meg pot
NPN 3904
B
C
E
PNP 3906B
C
E
+
47
10
0.1 F
ckt
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What if we need a special size capacitor? How to calculate size if in series or parallel.
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Backup slides
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What is an RC time constant ( sec?
After one time-constant (), the capacitor is ~ 63% discharged. After 5 time-constants (5), the capacitoris ~ 99% discharged. This chart can be used to help choose the size of capacitors and resistors that youwill need for projects you will do if you take Beginning Electronics later on.
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ES demo 8-4. Capacitor discharge after one time constant.
++ 4700 uf
VOM9 volts
Resistor value (ohms)Expected voltage at 1
Time ConstantExpected discharge time at 1 TC (sec)
Measured time until meter reads 3.4 volts
1,000 3.33 4.7
2,000 3.33 9.4
4700 3.33 22
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Hookup diagram for ES demo 8-4
push button switch
+4700 uf
R+
9.0
volts
:10 vdc
Volt
Meter
ckt