Which Cable, Where?

Almost every CBSE network case study asks you to suggest a wired medium. The right answer depends on two words in the question: is the link inside a campus or between cities, and does it ask for economical or fast?

1The three cables, side by side

Three cables, one noisy neighbour

Switch the noise on and watch the signal that arrives at the far end. Drag sideways to turn.

The three wired media, cut away. Switch the noise on and compare what arrives.

Twisted pair and co-axial shares come from the same models as their own lessons; the co-axial figure is a teaching figure.

	Twisted pair	Co-axial	Fibre-optic
Carries	Electric signals	Electric signals	Light
Made of	Pairs of twisted, insulated copper wires	Copper core, insulator, braided shield, cover	Glass core, cladding, jacket
Bandwidth	Lowest	Higher	Highest
Distance	Shortest (about 100 m per run)	Longer	Longest
Electrical noise	Reduced by the twist	Blocked by the braid	Not affected at all
Cost	Cheapest	More	Most expensive
Installing	Easiest: thin and flexible	Harder: thick and stiff	Hardest: fragile, needs special tools
Typical use	Telephone lines, LANs	Cable TV	Backbones, between cities and countries

2Choosing a wired medium in a case study

🏫 Inside a campus, “economically”

Twisted pair (Ethernet cable) — the cheapest. CBSE’s 2022-23 sample paper marking scheme answers “Ethernet Cable”.

🌆 Between cities, “fast / high-speed”

Optical fibre — highest bandwidth, longest distance. CBSE’s 2025-26 sample paper marking scheme answers “Optical Fibre”.

“Efficiently” inside a campus

When the question asks for the most efficient cable within a campus, CBSE’s own answers have differed. The 2024-25 sample paper’s marking scheme gave co-axial cable for the layout, and in the very next part said no repeater was needed because optical fibre carries data far further than the campus. Name the cable and give the reason: co-axial for better shielding and more bandwidth than twisted pair, or optical fibre for the highest speed and long distances between blocks.

3From the board papers

Write any two differences between fibre-optic cable and co-axial cable.CBSE compartment exam 2023

2 marks

▶Show the answer

Fibre-optic cable carries data as light through glass; co-axial cable carries electric signals through a copper core.
Fibre-optic cable has a higher bandwidth and carries signals over longer distances, and is not affected by electrical noise; co-axial cable has lower bandwidth and relies on its braided shield against noise.

Another point: fibre is more expensive and harder to install.

Name any two wired media that can be used to connect various computers of a block inside the Amritsar Campus.CBSE board exam 2026 (part of a case study)

1 mark

▶Show the answer

Any two of twisted pair cable, co-axial cable and fibre-optic cable.

Which among the following offers the maximum data transfer rate in a network? (a) Fiber optics (b) Twisted pair cable (c) Coaxial cable (d) UTPKV pre-board 2025-26, Bengaluru region

1 mark

▶Show the answer

(a) Fiber optics — highest bandwidth, so the highest data transfer rate. (UTP is a kind of twisted pair.)

4Check yourself

Quick Check

Which wired medium is NOT affected by a power cable running beside it?

Quick Check

Arrange the wired media from lowest to highest bandwidth.

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