Capacitors

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Capacitors
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Leyden Jar
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Leyden Jar Battery
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Capacitor Construction
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Capacitors
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Schematic of simple circuit with capacitor
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(No Transcript)
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Capacitor Charging
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Capacitor Charging
Current stops when capacitor is fully charged
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Capacitor Charging
Capacitor remains charged when power source is
removed
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Charging Capacitor Voltage
appliedvoltage
chargevoltage
Time
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Capacitor Discharging
Capacitor discharges when a current path is
applied
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Capacitor Discharging
Capacitor discharges when a current path is
applied
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Capacitor Discharging
Capacitor discharges when a current path is
applied
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Capacitor Discharging
Capacitor discharges when a current path is
applied
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Capacitor Discharging
Capacitor discharges when a current path is
applied
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Capacitor Discharging
Capacitor discharges when a current path is
applied
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Capacitor Discharging
Capacitor is fully discharged when plates are
neutral
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Time Constant

• Resistance is unavoidable in circuits, through
  the wire itself or through components such as
  resistors.
• Resistance introduces the element of time into
  charging and discharging a capacitor
• The voltage across a capacitor cannot change
  instantaneously because it takes finite time to
  move charge from one point to another.
• The rate at which a capacitor charges or
  discharges is determined by the time constant t
  RC (seconds)
• During one time constant interval, the charge on
  a capacitor changes approx. 63
• Five time constant intervals is accepted as the
  time to fully charge or discharge a capacitor and
  is called the transient time.

http//murray.newcastle.edu.au
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RC Time Constant

• Time (seconds) R (megohms) C (microfarads)

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of charge
time
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Charging Capacitor Voltage
appliedvoltage
chargevoltage
Time
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Charging Capacitor Voltage
appliedvoltage
resistance added
chargevoltage
Time
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Discharging Capacitor Voltage
appliedvoltage
chargevoltage
Time
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Discharging Capacitor Voltage
appliedvoltage
resistance added
chargevoltage
Time
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(No Transcript)
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Relay Circuit
6 V
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Relay Circuit
6 V
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Relay Circuit
When switch button is released, relay relaxes
6 V
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Relay Circuit w/capacitor
6 V
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Relay Circuit w/capacitor
6 V
Relay activates
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Relay Circuit w/capacitor
switch open
6 V
capacitor discharges through relay coil, which
maintains the magnetic field for a time
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Relay Circuit w/capacitor
switch open
6 V
Relay remains activated for a period of time
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Relay Circuit w/capacitor
6 V
Capacitor is discharged so relay relaxes