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This Material Is On The Class Site. Finishing Up on Capacitors. February 10. Howjado ?. Great Good Not So Good Bad Don’t turn your back!. What are we doing. Today Examination I Complete Capacitors Friday DC Circuits Play with batteries, wires and light bulbs Watch for WebAssign .
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This Material Is On The Class Site Finishing Up on Capacitors February 10 CAPACITORS
Howjado? • Great • Good • Not So Good • Bad • Don’t turn your back!
What are we doing • Today • Examination I • Complete Capacitors • Friday • DC Circuits Play with batteries, wires and light bulbs Watch for WebAssign . . . Next Week – More of the same
The Capacitor Real World Two pieces of metal close to one another but they don’t touch. Charge has no place to go!
String them together ….. Single Piece of Metal. Not connected to anything - - - - - - - - - - - - - - +++++++ +++++++ electrons electrons electrons
String them together ….. q -q q -q - - - - - - - - - - - - - - +++++++ +++++++ Charge is the same for every capacitor in a series “string”
String them together ….. C1 C2 q -q q -q - - - - - - - - - - - - - - +++++++ +++++++ Wires are equipotentials … sort of.
Two ways to go to the same place! C1 C2 V1 V2 q -q q -q - - - - - - - - - - - - - - +++++++ +++++++ VT
Working Together – But Separately! Model One Single Conductor
PARALLEL Calculate the combined capacitance C1= C2= C1||c2= C1 Measure=__ C2
SERIES (C1+C2)series=
Determine the equivalent capacitance between A and B for the group of capacitors in the drawing. Let C1 = 14 µF and C2 = 5.0 µF.
UNITS • A capacitor which acquires a charge of 1 coulomb on each plate with the application of one volt is defined to have a capacitance of 1 FARAD • One Farad is one Coulomb/Volt
Continuing… • The capacitance of a parallel plate capacitor depends only on the Area and separation between the plates. • C is dependent only on the geometry of the device!
What's Happening? DIELECTRIC
Apply an Electric Field Some LOCAL ordering Larger Scale Ordering
Adding things up.. - + Net effect REDUCES the field
We can measure the C of a capacitor (later) C0 = Vacuum or air Value C = With dielectric in place C=kC0