Download presentation

Presentation is loading. Please wait.

Published bySteven Pottinger Modified over 3 years ago

1
Capacitor

2
Construction A capacitor is a device that sores electrical charge. It is constructed of two parallel conductive plates separated by an insulating material called the dielectric.

3
How a capacitor stores charge No electrons flow through the dielectric because it is an insulator.

4
Basic Idea The Voltage across a capacitor CANNOT change instantaneously The charge/discharge current, however, can change instantaneously!

5
If the capacitor is disconnected from the source, it retains the stored charge for a long. Becareful when touching or handling capacitors in or out of a circuit. If you touch the leads, you may be in for a shock as the capacitor discharges through you.

6
C:The amount of charge that a capacitor can store per unit of voltage across its plates. – Simply put, capacitance is a measure of a capacitor’s ability to store charge – C=Q/V Units: – The farad (F) is the basic unit of capacitance. – Examples: MicroFarads, PicoFarads

7
How a capacitor stores energy A capacitor stores energy in the form of an electric field that is established by the Opposite charges stored on the two plates. The electric field is represented by lines of forces between the positive and negative charges.

8
What affects a capacitor’s ability to store charges? – Area – Distance between plates – Dielectric

9
Overlap area If you can move the effective plate area, you can make a variable capacitor.

10
Plate distance

11
Dielectric constant The presence of the dielectric material weakens the electric fields between the plates. So V is reduced. Since C=Q/V and Q=CV, C is increased for fixed Q.

12
Dielectric strength The dielectric also determines the maximum field strength that can be handled by a capacitor. – Air: 80 V/mil – Glass: 2000 V/mil

13
Dielectric properties MaterialDielectric Strength (V/mil)Dielectric constant (Relative Permitivity) Air801 Paper (paraffined)12002.5 Oil3754 Mica15005.0 Glass20007.5 Ceramic10001200 If you wish to conserve space, you may wish to use ceramic, but you might not be able to use it in high voltage applications.. If you wish to build capacitors for high voltage applications, you may choose glass, but your capacitors may be bulky..

14
Capacitance formula C=Aε/d

15
Capacitors Mica Capacitors Ceramic Capacitors Plastic Film Capacitors Electrolytic Capacitors

16
Mica Capacitors Typical range: 1 pF to 0.1 uF Stack capacitors in parallel to increase effective capacitance.

17
Ceramic capacitor More compact than Mica capacitors since ceramic dielectric has high dielectric constant. Range: 1 pF to 100 uF Voltage rating: up to 6000 V

18
A surface mount ceramic capacitor Note that the capacitors are connected in parallel

19
Plastic film capacitors You roll up the capacitor to increase capacitance

20
Electrolytic capacitor Straight plate is positive, the curved plate is negative. 1 uF to 200,000 uF.

21
Comparison CategoryRange Mica capacitors1 pF to 0.1 uF Voltage rating: 100 V to 2500 V dc. Ceramic capacitor1 pF to 100 uF. Voltage rating: up to 6000 V. Plastic Film capacitorsLess than 1 uF. Electrolytic capacitors1 uF up to 200,000 uF. 350 V is a typical maximum.

22
Caution http://www.youtube.com/watch?v=9j DsNe_bmtE http://www.youtube.com/watch?v=9j DsNe_bmtE How does it happen? – The reverse bias voltage destroys the dielectric material. – The capacitor will conduct short circuit current – The oxide will get oxidised, converted into oxygen gas, generating high pressure, and bursting open the capacitor.

23
Series Capacitance

24
Parallel Capacitance

Similar presentations

Presentation is loading. Please wait....

OK

Chapter 9 CAPACITOR.

Chapter 9 CAPACITOR.

© 2018 SlidePlayer.com Inc.

All rights reserved.

To ensure the functioning of the site, we use **cookies**. We share information about your activities on the site with our partners and Google partners: social networks and companies engaged in advertising and web analytics. For more information, see the Privacy Policy and Google Privacy & Terms.
Your consent to our cookies if you continue to use this website.

Ads by Google

Ppt on sf6 gas circuit breaker Ppt on current account deficit graph Best ppt on earth day Ppt on climate of india Ppt on nanotechnology Ppt on channels of distribution chart Ppt on tb treatment Ppt on principles of object-oriented programming for dummies Ppt on reuse of wastewater Ppt on higher education system in india