1. What is Cable Capacitance?

Cable capacitance refers to the ability of a coaxial cable to store electrical charge. It's an important parameter in cable design and affects signal transmission quality, especially in high-frequency applications.

2. How Does the Calculator Work?

The calculator uses the cable capacitance formula:

Where:

• \( C \) — Cable capacitance (Farads)
• \( \epsilon \) — Permittivity of the dielectric material (Farads/meter)
• \( l \) — Length of the cable (meters)
• \( b \) — Outer radius of the cable (meters)
• \( a \) — Inner radius of the cable (meters)

Explanation: The capacitance increases with higher permittivity and longer cable length, and decreases with larger ratio of outer to inner radius.

3. Importance of Cable Capacitance Calculation

Details: Cable capacitance affects signal quality, transmission speed, and power loss in cables. It's crucial for designing communication systems, power transmission lines, and electronic circuits.

4. Using the Calculator

Tips: Enter permittivity in F/m, length in meters, and both radii in meters. Ensure outer radius is greater than inner radius. All values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What is typical permittivity for common cable dielectrics?
A: PVC ≈ 3.4×10⁻¹¹ F/m, PE ≈ 2.25×10⁻¹¹ F/m, Teflon ≈ 2.1×10⁻¹¹ F/m, Air ≈ 8.85×10⁻¹² F/m.

Q2: How does capacitance affect signal transmission?
A: Higher capacitance causes more signal attenuation and distortion, especially at higher frequencies.

Q3: What are typical capacitance values for coaxial cables?
A: Common values range from 30-100 pF/ft (100-300 pF/m) depending on cable type.

Q4: Why does the ratio of radii affect capacitance?
A: The electric field is concentrated in the dielectric between conductors. Closer spacing (smaller b/a ratio) increases capacitance.

Q5: Can this formula be used for non-coaxial cables?
A: No, this formula is specific to coaxial cables. Other cable geometries require different formulas.