CHAPTER 1

Capacitor & Di-electric

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1 . 1 1 ) 2 1 . 3 1 . 4 1 ) 5

Capacitance Capacitor in series & parallel Strength stored in a charged capacitor Charging & discharging of capacitors Capacitors with dielectric

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1 ) 1 Capacitance

Learning Final results:

At the end with this topic, pupils should be able to: пѓј Define capacitance пѓј Make use of the capacitance solution пѓј Determine capacitance of parallel menu

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 A capacitor is electric element of store electric charge  It is composed two seite an seite conductors dishes, one efficiently charged as well as the other is definitely negatively charged  The 2 plates are placed parallel with one another at a little distance apart

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Mark

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 The performing plates could possibly be in the shape of: i. cylindrical ii. spherical iii. seite an seite plate

cylindrical

spherical

Parallel plate

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Charging & Discharging

 When a capacitor is linked to a circuit with Household power (DC) supply, two techniques, which are called " charging” and " discharging” the capacitor may happen i. Recharging process

пѓј

The capacitor is coupled to the DC power supply and current flows through the circuit

Asking process

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пѓј

Both plates find the equal and opposite charges and a growing potential difference, vc, is done while the capacitor is asking Once the ac electricity at the terminals of the capacitor, vc, is equal to the energy supply volts, vc = V, the capacitor can be fully incurred and the current stops streaming through the outlet

пѓј

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ii.

Preventing powering process

пѓј When the capacitor disconnected through the power supply, the capacitor is usually discharging through the Resistor RD and the voltage between the discs drops down gradually to zero, vc = 0

Discharging process

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 Figure below shows a great way of charging each dish by using a battery  If the battery is usually disconnected the charge stick to the discs  Electrical field is out there between the china which reveal the existence of potential difference (voltage) between the discs

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 Energy is now stored and ready to be used

 Dielectric materials are usually accustomed to fill the gap between plates, not only to stop the plates coming from collapsing nevertheless the materials possess properties which could enhance the features of the capacitors

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Ch a ur g i n g p 3rd there’s r o ce ss

capacitor

+

-

battery

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Use s o f ca g a ci t o r s

 Capacitors are commonly employed in many electric circuits  Examples: i. photoflash unit – capacitor store wide range of energy which can be released in a flash the moment triggered

ii. Radios, tvs, computers

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Capacitance

Definition: the amount of impose stored to each plate every unit volts applied across the plates C=Q V sign: C product: Coulomb = Farad (F) Volt Electronic +Q -Q

+

-

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Work out 1 1 ) When a potential difference of 24V is usually applied throughout a capacitor, the demand on the capacitor is a hundred and twenty ОјC. Precisely what is the capacitance of the capacitor? [Ans: 5x10-6] 2 . What is the fee on a three hundred pF capacitor when it is incurred to a volt quality of 1. 0 kV? [Ans: 3x10-7] several. What is the difference throughout a capacitor with 235 ОјC and 526 nF? [Ans: 446. 8]

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Pa ur a l l at the l - p d a big t e California p a ci t o ur s

 Consider a two parallel plates capacitor of equal area A will be separated with a distance g and the space between plates is vacuum/air: d + +Q + + & V

--

A

-Q

E

 When the capacitor is recharged, its dishes have fees of equivalent magnitudes yet opposite signs: + Q and −Q then the potential difference Sixth is v across the dishes is developed Miss Nor Amalina Ahmad 2012

 Since...

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