The document provides a brief history of capacitors, describing their invention by Ewald Georg von Kleist in 1745, Pieter van Musschenbroek's Leyden Jar in the same year, and Benjamin Franklin's experiments with storing charge. It explains that a capacitor consists of two conductors charged with equal and opposite charges that are separated by an insulator, and that a battery charges the plates by pulling electrons from the positive plate and depositing them on the negative plate. The capacitance of a capacitor depends on the area of the plates, distance between plates, and dielectric constant of the insulating material.

2. • First Capacitors
– Ewald Georg von Kleist (German)
A Little History
• 1745
– Pieter van Musschenbroek (Dutch)
• Leyden Jar
– Benjamin Franklin (American)
• Franklin Square
– Michael Faraday (English)
• Wanted to store unused electrons from
experiments
• Oil drums
• Unit of capacitance named after him

4. Capacitor
 2 conductors charged equal &
opposite separated by an insulator
+ – • Battery charges the plates until the
potential difference (voltage)
+ –
between them is equal to the voltage
+ – of the battery
+ – • These stay charged even after the
E battery is disconnected
• Battery pulls e’s from the + plate
and deposits them on the – plate.
Insulator blocks them from jumping
+ --
Battery back over.

5. Just a few questions:
1) What is flowing through the wire?
2) What function does the battery have?
3) Is this animation an accurate depiction of the
behavior of the electrons in the circuit?
+ e
--

6. Just a couple of questions:
1) Will the charges build up on the plates FOREVER?
2) When will the charges stop flowing?
3) Why don’t the charges jump from one plate to the other?
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ e-
-

7. Just one question:
1) What will happen to a light bulb if we include it in the
circuit?
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -
+ -

9. • Capacitance
Rating Capacitors
– The ratio of stored charge to the electric
potential difference QαV
Q Charge
Slope? = (Coulombs - C) Q = VC
V Potential
Difference Capacitance
Q (Volts - V) (Farads - F)
Summary of Variables & Units
Area under Q Charge C
curve? V Voltage (Electric V
Potential)
V 1
A = bh C Capacitance F
2
1 PC
E Potential Energy J
= QV
2 E Electric Field N/
C

10. • Capacitance
Rating Capacitors
– Also determined by the
construction of the capacitors
• Area of plates (A)
• Distance between plates (d)
• Type of insulator between plates
(ε r - dielectric constant)
– Plastic, glass, ceramic, paper
εo εrA
C=
d

11. • Prevent information loss
Where ARE THEY?!
– Supplies power while battery charges
• Car audio for amplifier
– Stores energy for demand
• Pulsed lasers
– High energy, short time lasers
• Weapon detonators
– nukes
• Flashes in cameras
– Listen to them whine
• Keyboards
– Changes distance between plates
• Fuel level detection in airplanes
– Changes properties of insulator (fuel)
• Defribulators
– Sends an instant discharge through the heart