Capacitance Converter

Convert between different units of electrical capacitance including farads, microfarads, nanofarads, and picofarads.

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Common Capacitance Conversions

Most Common Conversions

Historical & CGS Units

• Coulomb per Volt (C/V): Equivalent to the farad (1 F = 1 C/V by definition)
• Abfarad (abF): CGS electromagnetic unit = 10⁹ F (1 gigafarad)
• Statfarad (statF): CGS electrostatic unit ≈ 1.112650 × 10⁻¹² F

Typical Capacitor Values

• Ceramic capacitors: 1 pF - 1 μF (RF circuits, decoupling)
• Film capacitors: 100 pF - 10 μF (audio, timing circuits)
• Electrolytic capacitors: 1 μF - 10,000 μF (power supplies, filtering)
• Supercapacitors: 0.1 F - 3000 F (energy storage, backup power)
• Decoupling capacitors: 100 nF (0.1 μF) typical
• Timing capacitors (555 timer): 1 nF - 100 μF
• Crystal oscillator loading: 10-30 pF
• RF tuning capacitors: 1-500 pF

Real-World Examples

• Smartphone touch screen: ~10-50 pF per sensor node
• Computer motherboard decoupling: Hundreds of 100 nF capacitors
• Audio crossover (tweeter): 1-10 μF
• Power supply smoothing: 1000-4700 μF typical
• Camera flash: 100-300 μF at high voltage
• Car audio amplifier: 1-5 F (supercapacitor bank)
• Electric vehicle regenerative braking: 10-100 F modules
• PCB trace capacitance: ~1-2 pF per cm

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About Capacitance

Capacitance is the ability of a system to store electric charge. It is defined as the ratio of electric charge stored on a conductor to the electric potential difference (voltage) between the conductors.

The Farad (F)

The farad (F) is the SI unit of capacitance, named after English physicist Michael Faraday. One farad is defined as the capacitance of a capacitor that stores one coulomb of charge when a potential difference of one volt is applied across it:

1 F = 1 C/V = 1 s⁴·A²/(m²·kg)

Where:

• C = Coulomb (unit of electric charge)
• V = Volt (unit of electric potential)
• Q = Charge stored (coulombs)
• C = Capacitance (farads)

Capacitance Formula

The fundamental relationship between charge, capacitance, and voltage:

C = Q / V

For a parallel-plate capacitor:

C = ε₀ · εᵣ · A / d

Where:

• ε₀ = Permittivity of free space (8.854 × 10⁻¹² F/m)
• εᵣ = Relative permittivity (dielectric constant) of the material
• A = Area of the plates (m²)
• d = Distance between plates (m)

Why Farads Are Large

One farad is an extremely large capacitance for typical electronic components. A 1 F capacitor with a voltage rating of 1 V stores only 1 joule of energy, but it requires enormous plate area or extremely small separation. Most practical capacitors are measured in micro-, nano-, or picofarads.

To put it in perspective: A 1 F capacitor made from parallel plates 1 cm apart would need plates approximately 1,000 square kilometers in area!

Common Units in Electronics

• Picofarad (pF): Used for RF circuits, crystal oscillators, and parasitic capacitances
• Nanofarad (nF): Common in signal processing and timing circuits
• Microfarad (μF): The most commonly used unit in general electronics
• Millifarad (mF): Used in power electronics and audio applications
• Farad (F): Used for supercapacitors in energy storage applications

Capacitor Applications

• Energy Storage: Power supplies, flash photography, electric vehicles
• Filtering: Removing AC ripple from DC power, audio crossovers
• Coupling/Decoupling: Passing AC signals while blocking DC
• Timing: RC circuits, oscillators, delay circuits
• Tuning: Radio frequency selection, resonant circuits
• Power Factor Correction: Industrial motors and power systems
• Signal Processing: Filters, integrators, differentiators
• Touchscreens: Capacitive sensing for user input

Energy Stored in a Capacitor

The energy (E) stored in a capacitor is given by:

E = ½ C V²

Where:

• E = Energy (joules)
• C = Capacitance (farads)
• V = Voltage (volts)

Series and Parallel Capacitors

Parallel: Total capacitance is the sum of individual capacitances

C_total = C₁ + C₂ + C₃ + ...

Series: Reciprocal of total capacitance is the sum of reciprocals

1/C_total = 1/C₁ + 1/C₂ + 1/C₃ + ...

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