Tech.Skills.Capacitor.07.21.11
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Transcript of Tech.Skills.Capacitor.07.21.11
Electrical & Electronic Components
What is a capacitor
• A passive component designed for storing electric energy (charge)
• Increases efficiency of a circuit system
• Does not dissipate heat but stores energy
• Energy stored can be retrieved at a later time
• Blocks DC and permits AC to pass
Capacitors – electrical components
LSU 08/11/2004 Electronics 2 4
Capacitor types
Ceramic disk Monolithic ceramic
Dipped siver-mica
Mylar Mylar
Solid tantalum, polarized
Radial aluminum electrolytic
Axial aluminum electrolytic
Construction
• Consists of two conducting plates separated by an insulating layer called a dielectric.
• Differs in size, arrangements of plates and dielectric material
Application
• Communications• Instrumentations• Life support equipment• Computers• Power supply systems
Capacitance
• The measure of a capacitor in its ability to store electric charge
• Expressed in Farads (F)
• Electric charge stored is proportional to voltage supplied from Power Supply:
Q = CEQ = Charge stored
C = Capacitance
E = Voltage applied to capacitor
Charging a capacitor
Capacitor not charged yet :
• Capacitor not connected to power source (battery)
• No potential difference between plates
• Therefore no charges stored in capacitor
Charging…cont’d
Battery connected across capacitor:• Electrons flow to and from plates• Electrons cannot flow through
because of dielectric material• Counter emf (reactance) induced
on plates • Electrostatic field induced
between plates• Reactance level = Power Supply
no further flow of current
Charging…cont’d
Power Supply disconnected:• Capacitor retains charges
because of electrostatic force existing between plates
• Unequal charges on both negative & positive plates
• Capacitor is now a source of potential energy
Discharging a capacitor
Capacitor connected to other circuit:
• Electrons flow through from negative plated to positive plate
• Capacitor is discharging
Discharging…cont’d
Current will stop flowing when charges of both positive and negative plates are equal
Capacitor is fully discharged when there’s no more energy left
Capacitors in parallel circuits
• Able to store more charges
C = C1+C2+C3…
Capacitors in series circuits
• Able to store less charges
C = (C1xC2) / (C1+C2)