CBSE Class 12 Physics VBQs Communication System

Communication System

Question 1. During a class discussion regarding the bandwidth of transmission medium, group A was of the opinion that message signals could be transmitted at any bandwidth. They were not aware of the transmission media to be used. Group B gave information about the commonly used transmission media while group C informed about the government procedures to be followed.

(a) What was the information given by group B and group C?

(b) What values do you observe in this class discussion?

Answer:

Team Work, Togetherness, Awareness.

Question 2. Two students of class 12 were interested in doing a project on ‘transmitting signals of different frequencies’. They completed their project without any help but found that (i) the transmission is attenuated and (ii) the various information signals transmitted at low frequencies got mixed up.

(a) Identify the solution for the problem

(b) What values can we learn from those students?

Answer:

Eagerness / Curiosity to learn more and scientific attitude.

Question 3. A TV tower has a height of 70m with an average population density around the tower as 1000 per km-2. In about 5 years the CITY LIMIT the place doubled and the residents were not able to get the broadcast clearly. Niharika, a student, identified the problem and notified the Government saying that the height of the tower should be increased to double its coverage.

(a) By how much should the height of the tower be increased?

(b) What values would you appreciate in Niharika?

Answer:

Awareness, Concern for public and Helping the society / being helpful to the society, initiative.

Question 4. Raman went to the market to purchase a T.V. set. He got confused with so many features and functions of electronic appliances. He took the help of his friend Raman, a science student. Shankar explained him about the communication system, digital and analogue signals. This knowledge proved of great help to Raman in purchasing a colour T.V.

(a) What type of nature Sankar has?

(b) What do you mean by the term communication? Which types of signals are better?

Answer:

(a) Sandeep is friendly, helping and well aware having a vast knowledge of subject.

(b) Truthful, intact and speedy transfer of knowledge or data from one place to other is called Communication. Digital signals are better. These are disturbance free, clear and sharp.

Question 5. Chitra was watching her favorite TV serial suddenly the picture started shaking on TV screen. She asked her brother to check the dish antenna. Her brother found no problem in dish. Chitra noticed the same problem in TV picture again after some time. At the same time she heard the sound of low flying air craft passing over their house. She asked her brother again. He explained the cause of shaking picture on TV screen when air craft passes over head.

(a) Name the values used by Chitra’s brother?

(b) Why the picture on the TV screen was shaking when air craft was passing over head?

Answer:

(i) Critical thinking and problem solving

(ii) Low lying air crafts reflect TV signals. Due to interference between direct signal received by antenna and reflected signal the picture on TV shakes

Question 6. One day Ravi has observed that the radio in his uncle’ house was tuned. But two programmes were coming at a time. Then he opened the radio set and he adjusted the coil properly again it was closed by Rahul. Mention a) scientific value exhibited by Ravi. B) What is the property which he changed and how was it corrected?

Answer:

(a) Critical thinking and awareness of subject

Question 7. One morning during school assembly the S U P W teacher who looks after the microphone arrangement was absent. Principal felt inconvenient without microphone to run assembly program. Then a boy of class XII came up on the assembly and he set right the microphone by rotating the knob of the amplifier. Then it started to function properly and loudly. (a) Mention one problem that might have caused to the amplifier

(b) Write the values of the student shown in the above situation?

Answer:

(a) Mismatch of resistance of the amplifier with output

(b) Critical thinking and problem solving

Question 8. Television is theater at home. A TV is a basically a receiver which can be tuned to transmitter of our choice. Younger generation says that T V has merits for the society but elders do not agree to it.

Assuming yourself to be young and then old list two reasons favouring each concept.

Answer:

Young- It is the useful tool to gain knowledge through news media

Old : Children tend to over utilize the entertainment component.

Question 9. Kannan lives in a house which is located just beside of a hill in outskirts of the town. He is very interested to listen the music especially of Ghantasala. Recently he purchased a radio set but unluckily he is not able to listen the music. Then a student named Sushil who resides in the neighborhood adjusted by putting one long wire over a wall could succeed the music to listen.

(a) Explain what may be the reason for not being received the signal initially?

(b) What is the scientific attitude shown by the student in solving the above problem?

Answer:

(a) Problem in the receiving part.

(b)Awareness and Curiosity

Question 10. Rekha is a late riser. Her grandfather observes that she remains awake late night listening to radio on mobile is also a receiver. Where you have to listen and not to observe anything. Thus you’re capable of doing other things simultaneously. Rekha does not ignore her works. But her grandfather blames the FM radio which has made her late riser. What is FM? Why is her grandfather worried?

Answer:

Frequency Modulation

He fears distraction of concentration level.

Question 1. Raj was cycling from his village to a neighboring village. On the way ,he met an old man who was walking in the direction of the same neighboring village. Raj invited the old man to sit on his cycle and took him to the neighboring village. The old man got down from the cycle, thanked Raj and gave his blessings.

(a) What according to you, are the values displayed by Raj?

(b) Can you relate the given paragraph with the process of modulation?

Answer:

(a) Raj showed concern for the stranger and respect for the old age of the person.

(b) Just as the old man sat on the cycle the message signal is superposed on the carrier wave. The modulated carrier wave travels some distance and recovered at the receiver.

Question 2. Sudha was watching her favourite TV serial. Suddenly the picture started shaking on TV screen. She asked her brother to check the Dish antenna. Her brother Found no problem in Dish . Sudha noticed the same problem in TV picture again after some time . At the same time she heard the sound of flying aircraft passing over their house. She asked her brother again. He explained the cause of shaking picture on TV screen when aircraft passes over head.

(I) Write the values shown by Sudha and her brother.

(II) Why was picture on TV screen shaking when aircraft was passing over head.

Answer:.

Values displayed are curiosity, scientific awareness.The picture on TV screen was shaking when aircraft was passing over head because of distortion of signals produced by aircraft.

Question 3. Though Parminder ,a 12 years old boy, was playing with a ball yet the boredom was reflected on his face.He was unhappy as nobody was there to play with him. His elder brother Manjinder was observing Parminder. Manjinder invited Parminder to throw the ball towards him. Manjinder asked Parminder to roll the ball on the ground towards him in the air or to hit the ball towards the ceiling of the room and direct it towards him. Now, Parminder was thoroughly enjoying the game.

(a) What according to you are the values displayed by Manjinder?

(b) Can you relate the paragraph with some concept of communication system?

Answer:

(a) Manjinder shows concern for the state of mind of his younger brother. Manjinder aroused the interest of his younger brother by participating in the game.

(b) The given paragraph can be related with three modes of wave propagation – ground wave propagation, space wave propagation and sky wave propagation.

Question 1. Raj was cycling from his village to a neighboring village. On the way ,he met an old man who was walking in the direction of the same neighboring village. Raj invited the old man to sit on his cycle and took him to the neighboring village. The old man got down from the cycle, thanked Raj and gave his blessings.

(a) What according to you, are the values displayed by Raj?

(b) Can you relate the given paragraph with the process of modulation?

Ans 1. (a) Raj showed concern for the stranger and respect for the old age of the person.

 (b) Just as the old man sat on the cycle the message signal is superposed on the carrier wave. The modulated carrier wave travels some distance and recovered at the receiver.

Question 2. Sudha was watching her favourite TV serial. Suddenly the picture started shaking on TV screen. She asked her brother to check the Dish antenna. Her brother Found no problem in Dish . Sudha noticed the same problem in TV picture again after some time . At the same time she heard the sound of flying aircraft passing over their house. She asked her brother again. He explained the cause of shaking picture on TV screen when aircraft passes over head.

(I) Write the values shown by Sudha and her brother.

(II) Why was picture on TV screen shaking when aircraft was passing over head.

Ans 2.Values displayed are curiosity, scientific awareness.The picture on TV screen was shaking when aircraft was passing over head because of distortion of signals produced by aircraft.

Question 3. Though Parminder ,a 12 years old boy, was playing with a ball yet the boredom was reflected on his face.He was unhappy as nobody was there to play with him. His elder brother Manjinder was observing Parminder. Manjinder invited Parminder to throw the ball towards him. Manjinder asked Parminder to roll the ball on the ground towards him in the air or to hit the ball towards the ceiling of the room and direct it towards him. Now, Parminder was thoroughly enjoying the game.

(a) What according to you are the values displayed by Manjinder?

(b) Can you relate the paragraph with some concept of communication system?

Ans 3. (a) Manjinder shows concern for the state of mind of his younger brother. Manjinder aroused the interest of his younger brother by participating in the game.

(b) The given paragraph can be related with three modes of wave propagation – ground wave propagation, space wave propagation and sky wave propagation.