This document defines capacitors and discusses their construction and uses. It begins by defining a capacitor as a device that stores electric charge, and provides the capacitance equation. Capacitors consist of two metal plates separated by an insulator. Their capacitance depends on the area of the plates, the distance between them, and the dielectric material. Capacitors are used in applications like heart defibrillators, camera flashes, power supplies, and to eliminate sparking in ignition systems. The document also covers charging and discharging capacitors, parallel and series capacitor configurations, and examples of calculating capacitance and energy stored in capacitors.

1. Video
Capacitors
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2. Definition of capacitors
A capacitor is a device for storing electric
charge.
Capacitance equation
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V
Q
C 

3. 20/12/2014 Capacitors 3
 Example
A 10 F capacitor has 10 V across it. What quantity of
charge is stored in it?
μC100
1010 6





CVQ
V
Q
C

4. Construction
Basically, capacitors consists of two metal
plates separated by an insulator. The
insulator is called dielectric. (e.g.
polystyrene, oil or air)
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5. Parallel plate capacitor
Absolute permittivity 0 =
Relative permittivity r
Area A
Distance between its plates d
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d
A
d
A
C r
 0
(F/m)1085.8 12


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= Ɛ 𝑟

7. Example
A parallel plate capacitor consists of two
metal plates, each of area A=150 cm ,
separated by a vacuum gap d=0.60 cm
thick. What is the capacitance of this device
c=
Ɛ0Ɛ 𝑟 𝐴
𝑑
=
(8.85×10−12)(150×10−2)
(0.60×10−2)
= 2.213 × 10−9
= 2.213nf
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8. Types of capacitors
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Mica Ceramic Plastic film
Electrolytic Polyester Variable

9. Uses of capacitors
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Heart defibrillators Camera flash units radio receivers
to eliminate sparking
in automobile ignition
systems
filters in power
supplies

10. Charging and discharging capacitors
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63 %
37 %

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V
Experiment

12. Time constant
The time constant is used to measure how
long it takes to charge a capacitor through a
resistor.
Energy
The energy stored in capacitor will given by
this equation
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 = CR

13. Partner Work
Question 1
Calculate the time constant.
T = R × C
= (47Ω) (1000 F)
= 47000 s
Question 2
Calculate the energy stored in a
10 F capacitor when it is charged
to 100 V.
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J0005010010
2
1
2
1 22  CVW

14. Parallel capacitor
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321 QQQQ 
321 VVVV 
11
VCQ 
𝐶 𝑇 = 𝐶1 + 𝐶2 + 𝐶3

15. Series capacitor
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321 VVVV 
𝐶 𝑇 =
1
1
𝐶1
+
1
𝐶2
+
1
𝐶3
321 QQQQ 

16. Group Work
Question 1. Find the total capacitance of
the three capacitors connected in parallel
with a 24-V battery.
𝐶 𝑇 = 𝐶1 + 𝐶2 + 𝐶3
𝐶 𝑇 = 2𝜇𝐹 + 4𝜇𝐹 + 6𝜇𝐹
𝐶 𝑇 = 12𝜇𝐹
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17. Question 2. Find the total capacitance of
the three capacitors connected in series with
a 24-V battery.
𝐶 𝑇 =
1
1
𝐶1
+
1
𝐶2
+
1
𝐶3
𝐶 𝑇 =
1
1
2𝜇𝐹
+
1
4𝜇𝐹
+
1
6𝜇𝐹
𝐶 𝑇 = 1.09𝜇𝐹
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18. Thank You for your listening
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