Theory - 19 :- Capacitor, Working Principle, Its Uses, Unit, Types , Color Coding and Tolerance.

 A capacitor is a passive two-terminal electrical component used to store electrical energy in an electric field. It acts like a temporary, fast-discharge battery.

Working Principle

1. Construction: A capacitor consists of two conductive plates separated by an insulating material called a dielectric (e.g., air, paper, ceramic).

2. Charging: When connected to a voltage source (like a battery), the source draws electrons from one plate (making it positively charged) and deposits them onto the other plate (making it negatively charged).

3. Electric Field: The opposite charges on the plates are held in place by the non-conductive dielectric, creating an electric field that stores energy.

4. DC Block/AC Pass: In a DC circuit, once charged, the dielectric blocks the flow of current. In an AC circuit, the capacitor continuously charges and discharges as the voltage alternates, effectively appearing to pass the AC signal.

Capacitor Unit: Capacitance

Capacitance (C) is the measure of a capacitor's ability to store electric charge.

Certainly! Here is a concise overview of capacitor theory, working principles, uses, units, types, color coding, and tolerances.

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💡 Capacitor Theory and Working Principle

A capacitor is a passive two-terminal electrical component used to store electrical energy in an electric field. It acts like a temporary, fast-discharge battery.

Working Principle

1. Construction: A capacitor consists of two conductive plates separated by an insulating material called a dielectric (e.g., air, paper, ceramic).

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2. Charging: When connected to a voltage source (like a battery), the source draws electrons from one plate (making it positively charged) and deposits them onto the other plate (making it negatively charged).

3. Electric Field: The opposite charges on the plates are held in place by the non-conductive dielectric, creating an electric field that stores energy.

4. DC Block/AC Pass: In a DC circuit, once charged, the dielectric blocks the flow of current. In an AC circuit, the capacitor continuously charges and discharges as the voltage alternates, effectively appearing to pass the AC signal.

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📏 Capacitor Unit: Capacitance

Capacitance ($C$) is the measure of a capacitor's ability to store electric charge.

• Formula: $C = \frac{Q}{V}$

  • $C$: Capacitance

  • $Q$: Charge stored in Coulombs (C)

  • $V$: Voltage applied in Volts (V)

• Base Unit: The standard unit is the Farad (F).

• Practical Units: Since a Farad is a very large unit, practical capacitors are typically rated in smaller units:

  • Microfarad ($\mu$F): $10^{-6}$ F

  • Nanofarad (nF): $10^{-9}$ F

  • Picofarad (pF): $10^{-12}$ F

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🛠️ Uses of Capacitors

Capacitors are essential components in nearly all electronic circuits, used for:

• Energy Storage: Providing quick bursts of power (e.g., in a camera flash or a defibrillator).

• Filtering/Smoothing: Reducing voltage ripple in power supply circuits (like after a rectifier) to provide a smooth DC output.

• Timing: Used in combination with resistors to create time-delay circuits, oscillators, and clock generators (e.g., in 555 timers).

• Coupling/Decoupling (Bypassing): Coupling an AC signal from one stage to another while blocking DC. Decoupling (or bypass) to shunt high-frequency electrical noise to the ground.

• Tuning: Used in radio and filter circuits to select a specific frequency.

Type	Polarity	Dielectric Material	Key Characteristics & Common Uses
Electrolytic	Polarized	Aluminum Oxide, Tantalum Pentoxide	High capacitance values in small sizes. Used for power supply filtering and decoupling. Must be connected with correct polarity.
Ceramic	Non-Polarized	Ceramic	Small, inexpensive, wide range of values. Used for high-frequency decoupling and filtering.
Film (Mylar, Polyester)	Non-Polarized	Plastic Film (e.g., Polypropylene)	High stability, low tolerance, good for AC and timing circuits.
Mica	Non-Polarized	Mica	Excellent stability, high precision, low loss. Used in high-frequency / RF circuits.
Variable	Non-Polarized	Air, Plastic Film	Capacitance can be mechanically adjusted. Used for tuning radio circuits (tuning knobs).

🎨 Color Coding and Tolerances

Capacitor values are often printed directly on the body, especially for larger ones. For small components (like ceramic discs or older types), a three-digit alphanumeric code or a color code is used.

Alphanumeric Code (Most Common)

The code ABC J/K/M is common, where the value is in picofarads (pF):

1. A & B: First and second significant digits.

2. C: Multiplier (power of 10).

3. J/K/M: Tolerance letter (see table below).

Capacitor Color Code (Less Common, Older/Specific Types)

The color code is similar to a resistor code, often with 4 or 5 bands/dots. The value is usually in pF.

Tolerance

Tolerance indicates the allowable variation between the actual capacitance value and the nominal (marked) value, typically expressed as a percentage