capacitor

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capacitor. They are important in both electric & electronic circuit. Have you seen any of them before ?. Where can we find the capacitors ?. We can find it in radio, TV sets , and computers .
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capacitor They are important in both electric & electronic circuit
  • Have you seen any of them before ?
  • Where can we find the capacitors ? We can find it in radio, TV sets , and computers . Although there are many different types of capacitors , but they all work in the same way , and that which make it easy to use . Function : they all work in the same way , and that which make it easy to use .
  • 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 .
  • properties
  • All the capacitor have two leads the leads connect to two plates ,the conducting plates are separated by an insulating material which called the dielectric
  • The pates in capacitor need to have quite a large area plates ,the conducting plates are separated by an insulating material which called the dielectric
  • How is this achieved
  • By makes the insulator rolled up
  • Capacitors plates ,the conducting plates are separated by an insulating material which called the dielectric
  • In its simplest form, a capacitor consists of two metal plates, separated from each other by an insulator (air, mica, paper etc.)
  • A charged capacitor is shown below.
  • The capacitor plates have an equal but opposite charge of magnitude Q.
  • The net charge on the two plates is zero.
  • + Q +++++++ - Q ------- Charging a capacitor : plates ,the conducting plates are separated by an insulating material which called the dielectricWhat happens when the switch closed ? Discharging capacitor : plates ,the conducting plates are separated by an insulating material which called the dielectricif the battery is removed , we can discharge the capacitor + _ The charging & discharging processes happen very quickly .Can we show them down ? Chart .Can we show them down ? Q Charging Q Discharging t t Why does the direction of charging current in the opposite way of current of the battery ? Q way of current of the battery ?
  • Why current equal zero ?
  • Because p.d of battery =p.d of capacitor but in opposite direction
  • The charging & discharging processes happen very quickly .Can we slow them down ?
  • (if we place a resistor in series with capacitor the capacitor charge and discharges more slowly
  • Also we put a variable resistor to keep the current in steady value
  • Capacitance .Can we slow them down ?
  • The ability of a capacitor to store charge on its plates.
  • 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
  • Solve example1 page 267
  • How can we measured the charge on the capacitor plates ? stores for each volt applied across its plates . In fact : i.t=q Measuring capacitance : stores for each volt applied across its plates . In fact : Complete the table : stores for each volt applied across its plates . In fact :
  • A B stores for each volt applied across its plates . In fact :
  • Questions : stores for each volt applied across its plates . In fact :
  • Q1:What happens to the capacitor when the switch in position A?
  • Q2:What happens if you move the switch to position B?
  • Q3:Where did this energy come from ?
  • The energy of a charged capacitor stores for each volt applied across its plates . In fact :
  • 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
  • Q1 stores for each volt applied across its plates . In fact :
  • 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?
  • Use these link to find more about our lessons stores for each volt applied across its plates . In fact :
  • http://electronics.howstuffworks.com/solid-state-electronics-channel.htm
  • http://us.c2w.com/quizzes/45045-capacitor-quiz Capacitor in parallel stores for each volt applied across its plates . In fact : Here are 3 facts that you should know for capacitors in parallel
  • 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
  • Capacitor in series parallel Here are 3 facts that you should know for parallel
  • 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
  • Qs. parallel
  • Q1: Calculate the charge on each capacitor in this diagram :
  • If :
  • V=5volt
  • C1=500 micro farad C2=300 micro farad
  • Home Work : parallel Pg. 273 , Q :1-3-4-5-6
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