1. Definition & Determination of Capacitance
Definition of Capacitance
Uses for Capacitors
Capacitor Symbology
Properties of a Capacitor
Determination of Capacitance

2. Capacitors A capacitor is a device which stores electric charge on two
conducting plates, separated
by a finite gap.
Electric potential energy is stored in a uniform electric field, generated by the charge distribution on the two plates

3. Uses for Capacitors
Capacitors are used to dissipate electric energy to run a camera flash
A capacitor can provide energy to back-up computer power supplies
Capacitors can block low frequency AC signals, and act as power supply filters

4. Capacitor Symbology Capacitor schematic symbols
vs. Battery schematic symbol

5. Properties of a Capacitor
When a capacitor is connected to a source of potential difference (battery), the electrons are drawn to the (+) terminal of the battery & flow to the other plate, until equilibrium has been reached

6. Properties of a Capacitor
The electron debt on the LH plate leaves the plate with a net (+) charge. The excess electrons on the RH plate leaves the plate with a net (-) charge.
+Q Q
The establishment of this charge
distribution leads to the development
of a uniform electric field between the
plates

7. Capacitance Parameters
The amount of potential difference (ΔV) that can be applied across the plates is limited by the amount of charge that can be accumulated on the plates & is given by the relationship:
SI Units: Farads (1μF = 1.0 x 10-6 F)

8. Determination of Capacitance
The electric field between the plates
Is mostly uniform
The capacitance does not depend on Q or ΔV but only on the geometry of the device

9. The Coaxial Capacitor

10. Capacitance of Parallel Conducting Wires
2 conducting wires, of radius R, and length l