---
title: "Why wires are twisted in twisted pair"
subject: "Data Communication"
chapter: 4
key: "semester_5/data_communication:twisted-pair-why-twist"
source: https://www.bctengineer.com/q/semester_5/data_communication/twisted-pair-why-twist
site: BCT Engineering
---

# Why wires are twisted in twisted pair

Data Communication · Chapter 4: Transmission Media

- Asked in: 2069 Asar, 2 marks
- Video: [Why Are Cables Twisted? Twisted Pair Wires Explained](https://www.youtube.com/watch?v=RVzM-b3okH0) — Techi Tube
- Answer checked by Claude Sonnet 5.5 on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_5/data_communication/twisted-pair-why-twist
- Whole chapter: https://www.bctengineer.com/md/semester_5/data_communication/chapter-4

## Question

Why do we twist two wires in twisted pair cable?

## Short answer

Twisting ensures both wires receive nearly equal electromagnetic interference, which cancels out at the differential receiver. It also reduces crosstalk between pairs, and more twists per meter improve performance.

## Answer

Two parallel wires act as an antenna. Each picks up external electromagnetic interference and also radiates, causing crosstalk with neighbouring pairs.

When the two wires are twisted, each wire is alternately closer to the noise source and then farther from it. Both wires therefore pick up almost the same amount of noise. The receiver uses the difference of the two wire voltages (a differential receiver), so this equal noise cancels out. The twisting also reduces crosstalk between adjacent pairs, and more twists per metre give better performance (higher category cables).

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What problem do two parallel wires have?
   A. They act as an antenna, picking up interference and causing crosstalk
   B. They carry light
   C. They are too thick
   D. They have no resistance
   Answer: A. Parallel wires pick up and radiate EMI. (Key point: Problem)

2. How does twisting cancel noise?
   A. Twisting amplifies the signal
   B. Noise induced in both wires is nearly equal and the differential receiver cancels it
   C. Twisting adds a shield
   D. Twisting removes copper resistance
   Answer: B. The receiver uses the difference of the two voltages. (Key point: Cancellation)

3. What does more twists per metre give?
   A. More attenuation
   B. Worse crosstalk
   C. Better performance (higher category cables)
   D. Longer wires only
   Answer: C. Higher categories have tighter twists. (Key point: Twist rate)

## Related in Data Communication

- [Optical fiber advantages over coax and twisted pair](https://www.bctengineer.com/question.md?key=semester_5%2Fdata_communication%3Afiber-advantages) — Data Communication, chapter 4, asked 3×

## Related in other subjects

- [Radio signal in twisted pair and coaxial cable](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aradio-signal-twisted-coaxial) — Telecommunications, chapter 2
- [Full duplex on a single twisted pair](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Atwisted-pair-full-duplex-converter) — Telecommunications, chapter 2
- [Compare twisted pair, coaxial, fiber](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Acompare-twisted-coax-fiber) — Computer Networks and Security, chapter 2
- [T/F: two earth wires for double circuit](https://www.bctengineer.com/question.md?key=semester_8%2Ftransmission_and_distribution_system_design%3Atf-double-circuit-two-earth-wires) — Transmission and Distribution System Design, chapter 3