What is the significance of capacitance in Cables?

Question

What is the significance of capacitance in Cables?

Answer 1

  The capacitance is a characteristic of the ratio of the dielectric and the conductors.

  TV cables have a CI of 75 ohms,this produces the least loss to TV signals in the range of 30 to 900 megs,the least loss beginning at 30 meg.

  The characteristic impedance must be kept within a few ohms say 72 to 75.

  Computer cables with high speed data will only work over the coax cables at a CI imp of 50 ohms.any deviation of just a few ohms will corrupt the digital information intermittently causing unacceptable  errors.

Answer 2

From "Christian A"'s answer I think the relevant point is that cables are often inductive, so capacitance may help the power factor.

If the cable is for data communications, then capacitance can be a problem as it tends to be shunt capacitance, ie the signal out the other end decreases and has a low pass characteristic.

For slower work, the capacitance takes time to charge, the low pass character makes it difficult to put sharp edges through the cable.

Again, if the cable is used for data communications, then the combination of the cable inductance & capacitance means that the cable has a characteristic impedance: it becomes a transmission line.

Coaxial cables to antennas are often impedances like 50 Ohms or 75 Ohms.  

This means that to get power into the cable & out again, efficiently, matching the impedance is useful.

Similarly, it means that pieces of such cable can be used to create filters, and matching sections, as often used for tuning antennas for radio. For example by cutting quarter-wave sections & connecting them appropriately.

Answer 3

capacitance improves the power factor of the system

Answer 4

It depends on the type of cable and how it is being used.

Power transmission cables, capacitance causes power loss.

Power cables for short to medium distances, capacitance has little or no effect.

Audio signal shielded cables, capacitance acts as a filter that shunts higher frequencies to ground. This is countered by using a lower driving impedance.

Digital signal cables, twisted pairs, capacitance acts as a filter that shunts higher frequencies to ground and degrades rising and falling edges. This is countered by controlling the characteristic impedance of the cable, and using that as a source impedance.

RF signal cables, coaxial. capacitance acts as a filter that shunts higher frequencies to ground and degrades high frequencies. This is countered by controlling the characteristic impedance of the cable, and using that as a source impedance and receiver impedance.

.