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capacitor

capacitor. They are important in both electric & electronic circuit. Have you seen any of them before ?. Function :. Capacitors can store and then release electrical energy . The value of a capacitors is often measured in micro-farads .

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capacitor

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  1. capacitor

  2. They are important in both electric & electronic circuit • Have you seen any of them before ?

  3. Function : • Capacitors can store and then release electrical energy . • The value of a capacitors is often measured in micro-farads . • The amount of energy stored by the capacitor depends on : How much charged is moved on to the plates .

  4. The conducting plates are separated by an insulating material which is called the Dielectric

  5. Charging a capacitor :What happens when the switch closed ?

  6. Discharging capacitor :if the battery is removed , we can discharge the capacitor + _

  7. Why does the direction of charging current in the opposite way of current of the battery ?

  8. The charging & discharging processes happen very quickly .Can we slow them down ?

  9. Capacitance • The ability of a capacitor to store charge on its plates.

  10. The large the capacitance , the more charge the capacitor stores for each volt applied across its plates . In fact : • Capacitance = charge / voltage • C = Q / V

  11. How can we measured the charge on the capacitor plates ?

  12. Measuring capacitance :

  13. Complete the table :

  14. The energy of a charged capacitor • A B

  15. Questions : • Q1:What happens to the switch in position A? • Q2:What happens to the switch in position B? • Q3:Where did this energy come from ?

  16. The p.d. across the capacitor and the size of its capacitance , both affect the energy stored . • Energy stored =0.5Xcapacitance X (voltage)2 W = 0.5 X C X V2 OR W = 0.5 X Q X V

  17. Q1 • A capacitor is charged using a current of 20µA from a 5volts supply .After 55s it is fully charged. • Calculate : • A. Q? • B. C? • C. W?

  18. More Qs. • http://electronics.howstuffworks.com/solid-state-electronics-channel.htm http://us.c2w.com/quizzes/45045-capacitor-quiz

  19. Capacitor in parallel

  20. Here are 3 facts that you should know for • The p.d. across each capacitors is the same & equal to V . • The total Q is the sum Q = Q1+Q2 • The total C is the sum C = C1+C2 Q = C V

  21. Capacitor in series

  22. Here are 3 facts that you should know for • The Q. across each capacitors is the same & equal to Q . • The total V is the sum V= V1+V2 • The total C is the sum 1/C = 1/C1+ 1/C2

  23. Qs. • Q1: Calculate the charge on each capacitor in this diagram : • If : • V=5volt • C1=500 micro farad C2=300 micro farad

  24. Qs.: Pg. 273 , Q:6 Home Work : Pg. 273 , Q :1-3-4-5

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