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Electrical Capacitors

Electrical Capacitors

What are Capacitors?

Capacitors are electronic components that store electrical energy in a temporary electric field. They primarily consist of:

  • Two conductive plates (usually metal)
  • An insulating material between them called the dielectric

How do they work?

When connecting a capacitor to a power source:
1. Electric charges accumulate on the plates
2. Energy is stored in the electric field between the plates
3. This energy can be discharged when needed

Common Uses:

  • Smoothing electrical signals
  • Frequency filtering in circuits
  • Temporary energy storage (like camera flashes)
  • Circuit timing (with resistors)

Types of Capacitors:

  1. Ceramic capacitors (small size)
  2. Electrolytic capacitors (polarized - high capacity)
  3. Tantalum capacitors (better performance than electrolytic)
  4. Variable capacitors (adjustable capacity)

Important Terms:

Capacitance
Measured in Farads (F) - indicates storage capacity
Operating Voltage
Maximum voltage that can be applied to the capacitor
Tolerance
Percentage deviation from nominal capacitance

Capacitance Equation:

\[ C = ε₀εᵣ\frac{A}{d}\]
Where:
ε₀ = Permittivity of free space
εᵣ = Relative permittivity of the dielectric
A = Plate area
d = Distance between plates

Parallel Plate Capacitance Calculation

Parallel Plate Capacitance Calculation

↪ Capacitors are essential components in all modern electronic devices!

Series Connection of Parallel Plate Capacitors

✵ Series Connection:


When connecting capacitors in series
The first plate of the capacitor is connected to the second plate of the next capacitor
  • The charge on all capacitors is equal \[Q_{total} = Q_1 = Q_2=Q_3= ..\] The total voltage is the sum of individual voltages \[V_{total} = V_1 + V_2+V_3 + ...\]

    ✵ Equations:

    Total capacitance \[C_{total}\] in series connection \[\frac{1}{C_{total}}= \frac{1}{C_1 }+ \frac{1}{C_2 }+\frac{1}{C_3 }+ ... + \frac{1}{C_n }\]

    Where:

      \[C_{total}\] Total capacitance (Farad) \[C_1\;\;\;\;,\;\;\;\; C_2\;\;\;\;,\;\;\;\;C_3, ...\] Individual capacitor capacitances

      ✵ Practical Example:

      If we have two capacitors with capacitance \[C_1=4\;μF\;\;\;\;,\;\;\;\; C_2=6\;μF\] connected in series \[\frac{1}{C_{total}} = \frac{1}{4 }+\frac{1} {6} = \frac{3 + 2}{12} =\frac{5}{12}\] \[ C_{total} = \frac{12}{5 }= 2.4μF\]

      ✵ Important Notes:

      • The total capacitance in series connection is always less than the smallest capacitance in the circuit.
      • This type of connection is used to withstand high voltages.

      Series Capacitors Simulation

      Parallel Capacitor Connection

      ✵ Parallel Connection:


      When connecting capacitors in parallel
      The first plate of the capacitor is connected to the first plate of the next capacitor and to one battery terminal
      The second plate of the capacitor is connected to the second plate of the next capacitor and to the other battery terminal

      Parallel Connection Characteristics:

      The voltage across all capacitors is equal \[V_{total} = V_1 = V_2=V_3= ..\] Electric charges are distributed across capacitors \[Q_{total} = Q_1 + Q_2+Q_3 + ...\]

      ✵ Equations:

      Total capacitance \[C_{total}\] in parallel connection \[C{total}= {C_1 }+ {C_2 }+{C_3 }+ ... + \frac{1}{C_n }\]

      Where:

        \[C_{total}\] Total capacitance (Farad) \[C_1\;\;\;\;,\;\;\;\; C_2\;\;\;\;,\;\;\;\;C_3, ...\] Individual capacitor capacitances

        Practical Example:

        If we have three capacitors with capacitance \[C_1=4\;μF\;\;\;\;,\;\;\;\; C_2=6\;μF\;\;\;\;,\;\;\;\;C_3=2\;μF\] connected in parallel \[C_{tot}=C_1+C_2+C_3=4μF+6μF+2μF=12μF\]

        ✵ Important Notes:

        • The total capacitance in parallel connection is always greater than any individual capacitance in the circuit.
        • This type of connection is used in energy storage systems for electronic devices.
        • This type of connection is used in timing and filtering circuits.
        • This type of connection is used in solar power systems.
        Parallel Capacitance Calculator

        Parallel Capacitance Calculator

        Voltage (Volts):

        Capacitor Values (Farad):






        Capacitor Charging and Discharging

        ✵ Capacitor Charging and Discharging:

        1. Charging Process

        When closing the electrical circuit:

        • Electrons begin moving from the source (battery)
        • Charges accumulate on the capacitor plates
        • An electric field forms between the plates
        • Current gradually decreases until it stops completely

        Voltage across the capacitor\[V_C(t) = V_0(1 - e^{\frac{-t}{RC}})\]

        2. Discharging Process

        When opening the circuit:

        • The stored charges act as an energy source
        • Current flows in the opposite direction
        • Charge decreases exponentially with time
        • Voltage drops until reaching zero

        Discharging equation:\[ V_C(t) = V_0( e^{\frac{-t}{RC}})\]

        Important Notes:

        1. The time constant (Ï„ = RC) determines the process speed
        2. Capacitance (C) determines the amount of stored charge
        3. Resistance (R) affects the charging/discharging rate

        Practical Applications:

        • Electronic timing circuits
        • Emergency lighting systems
        • Current filters in power supplies


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