Chapter 24

Chapter 24

~ Capacitor: # Capacitor is a device that can store electric charges and consists of two parallel conducting plates placed near each other separating by dielectric material (insulator). # The important use is storing charges for late use such as in camera flash for example . #Capacitors; Parallel plates. Cylindrically shaped. Spherically shaped. # The symbol of a capacitor is #The symbol of a battery (which is n source of voltage) is

# Charging a capacitor by connecting the two plates to a battery.

Where C is the costant of proportionality and is called the capacitance of The capacitor, therefore C = Q/V coulomb/volt (Farad) The standard unit of the capacitance is Farad and it is so big, and the smaller units are : 1) micro farad 1MF=10-6F 2) pico farad

1PF=10-12F

Note: C does not depend on Q or V but it depends on the following factors: 1) The area of the two plates (A), 2) The distance separates the two plates (d) , 3)The insulatoer material between the plates. Determination C:

1) 2)

C = Q/V or C = 0 ‫ ع‬A/d for parallel plate capacitor .

#Connecting capacitors: Connecting in series: Qeq= Q1=Q2=Q3 Veq= V1+ V2+ V3 1/ Ceq= 1/ C1+ 1/ C2+ 1/ C3

#Connecting in parallel: Qeq= Q1+ Q2 +Q3 Veq= V1= V2= V3 Ceq= C1+ C2 +C3

Dielectric: # Dielectric is the insulating material separates the two parallel plates in the capacitor. # k= C/Co where k is the dielectric constant of the material separated the two plates.