This page contains the NCERT Computer Science class 12 chapter 11 Data Communication. You can find the solutions for the chapter 11 of NCERT class 12 Computer Science Exercise. So is the case if you are looking for NCERT class 12 Computer Science related topic Data Communication questions and answers for the Exercise
Exercise
Question 1
1. What is data communication? What are the main components of data communication?
Answer 1
Data communication means the exchange of data (text, image, audio, video, etc.) between two or more networked/connected devices using a communication medium.
Main components of data communication:
1.
Sender – device that sends data (computer, mobile phone, smartwatch, etc.).
2.
Receiver – device that receives data (computer, printer, laptop, TV, etc.).
3.
Message – the data/information to be exchanged (text, number, image, audio, video, multimedia).
4.
Communication medium / Transmission media – the path/link through which message travels (wired or wireless).
5.
Protocols – the set of rules that sender/receiver follow for successful and reliable communication (e.g., Ethernet, HTTP).
Question 2
2. Which communication mode allows communication in both directions simultaneously?
Answer 2
Full-duplex communication allows communication in both directions simultaneously (both devices can send and receive at the same time).
Question 3
3. Among LAN, MAN, and WAN, which has the highest speed and which one can cover the largest area?
Answer 3
•
Highest speed (generally): LAN
•
Largest area coverage: WAN
•
MAN is in between LAN and WAN.
Question 4
4. What are three categories of wired media? Explain them.
Answer 4
Three commonly used wired (guided) transmission media are: Twisted pair cable, Coaxial cable, Fiber optic cable.
(A) Twisted Pair Cable
•
Consists of two copper wires twisted (like a DNA helix).
•
Twisting helps reduce electrical interference.
•
Less expensive, commonly used in telephone lines and LANs.
•
Types: UTP and STP.
(B) Coaxial Cable
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Has a copper core, insulation, and an outer conductor (mesh) with plastic cover.
•
Better shielded and has more bandwidth than twisted pair.
•
Used for higher frequency signals over longer distance.
(C) Optical Fibre Cable
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Carries data as light inside a thin glass fibre.
•
Has higher bandwidth, supports higher data transfer rate, longer distance, and is not affected by electromagnetic noise.
•
It is expensive and unidirectional; for full duplex, two cables are required.
Question 5
5. Compare wired and wireless media.
Answer 5
Basis
Wired Media (Guided Transmission Media)
Wireless Media (Unguided Transmission Media)
Meaning
Data signals travel through a physical path / physical link.
Data signals travel through air as electromagnetic waves, using an antenna.
Medium used
Uses cables/wires (guided).
Uses free space (air) (unguided).
Examples
Twisted pair cable, Coaxial cable, Optical fibre cable.
Radio waves, Microwaves, Infrared (wireless transmission).
Typical uses (from chapter examples)
Twisted pair is used in telephone lines and LANs.
Wireless technologies like Bluetooth, WiFi and WiMax use unguided media.
Question 6
6. Which transmission media carries signals in the form of light?
Answer 6
Optical fibre cable carries signals in the form of light.
Question 7
7. List out the advantages and disadvantages of optical fiber cable.
Answer 7
✅ Advantages of Optical Fibre Cable
1.
Light weight: Optical fibre cables are light in weight, so they are easier to handle and install compared to many other cables.
2.
Higher bandwidth → Higher data transfer rate: Optical fibre provides higher bandwidth, which means it can carry more data. Because of this, it supports a higher data transfer rate.
3.
Longer distance transmission: Signals can travel for longer distances through optical fibre without needing frequent boosting/repeating.
4.
Not affected by electromagnetic noise: Optical fibre is not affected by electromagnetic noise, so the transmission is more reliable even in places where electrical interference is present.
❌ Disadvantages of Optical Fibre Cable
1.
Expensive: Optical fibre is costly, so the overall setup and maintenance can be more expensive.
2.
Unidirectional: A single optical fibre cable is unidirectional, meaning it carries signals in one direction only.
3.
Two cables needed for full duplex: For full duplex communication, two separate optical fibre cables are required—one for each direction.
Question 8
8. What is the range of frequency for radio waves?
Answer 8
The frequency range for radio waves is 3 KHz to 1 GHz.
Question 9
9. 18 Gbps is equal to how many Bits per second?
Answer 9
18 Gbps
= 18 × 230 bps
= 18 × 1,073,741,824 bps
= 19,327,352,832 bps
Note: It is given in the book that 1 Gbps = 230 bps.
Question 10
10. HTTP stands for?
Answer 10
HTTP stands for HyperText Transfer Protocol.
Question 11
11. Write short note on the following:
a)
HTTP
b)
Bandwidth
c)
Bluetooth
d)
DNS
e)
Data transfer rate
Answer 11
(a)
HTTP
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HTTP stands for HyperText Transfer Protocol.
•
It is the primary protocol used to access the World Wide Web (WWW).
•
HTTP works as a request–response (client-server) protocol and runs over TCP.
•
The common use is between a web browser (client) and a web server (server).
•
It defines how information is formatted and transmitted, and how servers/browsers should respond.
(b)
Bandwidth
•
Bandwidth is the range of frequencies available for transmitting data through a channel.
•
Higher bandwidth means higher data transfer rate.
•
Normally, bandwidth is the difference between maximum and minimum frequency in a composite signal.
•
Bandwidth is measured in Hertz (Hz).
(c)
Bluetooth
•
Bluetooth is a short-range wireless technology used to connect devices like mobile phones, mouse, headphones, keyboards, computers, etc.
•
Bluetooth-enabled devices use a low-cost transceiver chip and work in the unlicensed 2.4 GHz frequency band.
•
Typical range is about 10 meters with speed around 1–2 Mbps.
•
Devices within 10 meters form a piconet (personal area network).
•
A piconet works in master–slave configuration; one master can communicate with up to 7 active slave devices at the same time.
(d)
DNS
•
DNS stands for Domain Name System.
•
It is a system that translates (maps) domain names like
www.example.com into their corresponding IP addresses (for example, 93.184.216.34).•
This is needed because computers/devices communicate on a network using IP addresses, but humans find names easier to remember.
•
DNS works like a phonebook of the Internet: you give a name, and it returns the matching IP address.
•
Example: When you type
www.google.com in a browser, DNS helps find the correct IP address of Google’s server so the browser can connect to it.(e)
Data transfer rate
•
Data travels as signals over a channel, and one signal can carry one or more bits.
•
Data transfer rate is the number of bits transmitted between source and destination in one second.
•
It is also called bit rate.
•
It is measured in bits per second (bps), with higher units Kbps, Mbps, Gbps, Tbps.
Question 12
12. What is protocol in data communication? Explain with an example.
Answer 12
A protocol is a set of rules that sender and receiver follow so that data communication is successful and reliable. In other words, it tells how data will be sent, received, and understood between connected devices.
Example:
HTTP (HyperText Transfer Protocol) is a protocol used on the World Wide Web. It works between a web browser (client) and a web server (server) in a request–response manner (and it runs over TCP).
Question 13
13. A composite signal contains frequencies between 500 MHz and 1GHz. What is the bandwidth of a signal?
Answer 13
Bandwidth = maximum frequency − minimum frequency.
•
Maximum = 1 GHz = 1000 MHz
•
Minimum = 500 MHz
•
Bandwidth = 1000 − 500 = 500 MHz