definition & determination of capacitance definition of capacitance uses for capacitors...
TRANSCRIPT
Definition & Determination of Capacitance
• Definition of Capacitance
• Uses for Capacitors
• Capacitor Symbology
• Properties of a Capacitor
• Determination of Capacitance
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
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
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
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
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)
V
QC
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
area
echiswhere
A
QE
arg1
00
A
QddEV
0
d
A
V
QC 0