CBSE 12th Standard Physics Subject Value Based Questions 3 Mark Questions 2021 Part - I
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CBSE 12th Standard Physics Subject Value Based Questions 3 Mark Questions 2021 Part - I
12th Standard CBSE
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Reg.No. :
Physics
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While watching Discovery channel Sheela was impressed that certain organisms have the ability to sense the field lines of earth's magnetic field. They use this ability to travel from one location to another, Sheela wanted to find the angle of dip at her place. She then mounted the compass on a cardboard and placed it vertically along the magnetic meridian. She was able to measure the angle of dip
(a) What values did Sheela have?
(b) Define the magnetic element of earth.(a) -
Rita noticed that the transformer in her locality gets damaged quite often leading to long power cuts. She complained to the power distribution company with the help of her father and got the transformer replaced?
(i) What is the principle of a transformer?
(ii) Mention two losses which take place in a transformer.
(iii) Values exhibited by Rita in dealing with the above situation.(a) -
Sumeet a 5th class student observed a coloured film of oil on water when illuminated by white light. He felt happy and surprised to see this. His teacher explained him the reason behind it. The child then gives an example of spreading of kerosene oil on water to prevent malaria and dengue.
(i) What value was displayed by his teacher?
(ii) Name the phenomenon involved.(a) -
Physics teacher in the semiconductor chapter explained that a very low voltage is required for the operation of semiconductor diodes, but Ramesh found that at home the supply used for charging mobile or CD player etc. is 220V. He was confused. Then, he discussed this problem with his classmates and with the teacher. The teacher explained the reason and Mohan was satisfied.
(a) Why is 220V ac supply used in charger and CD player?
(b) What values were displayed by Mohan?(a) -
Demodulation is the reverse process of modulation, which is performed in a receiver to recover the original modulating signals. At the receiving end, the signals are generally weak due to attenuation in the channel. The receiver selects only the desired signal, rejecting the unwanted (noise) signals and amplifies the same.
Read the above passage and answer the following questions:
(i) What are the main functions of a demodulator?
(ii) Give any two examples of demodulators.
(iii) What does the phenomenon of demodulation imply in day to day life?(a)
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CBSE 12th Standard Physics Subject Value Based Questions 3 Mark Questions 2021 Part - I Answer Keys
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(a) The values showed by Sheela were nature of appreciation, curiosity, diligence, and creative skill
(b)There are three magnetic elements of earth magnetic field.
(i) Declination at a place is the angle between magnetic and geographical meridian at that place.
(ii) Magnetic dip or inclination is the angle which the strength of earth's magnetic field makes with its horizontal component in the magnetic meridian.
(iii) Horizontal component of earth's magnetic field is the component of total intensity of earth's magnetic field in the horizontal direction in the magnetic meridian. -
(i) Transformer is based on the principle of mutual induction i.e whenever magnetic flux linked with a coil is changed an induced emf is produced in the neighboring coil.
(ii) Transformer losses are copper loss and humming loss.
(iii) Value points are social awareness, responsive behavior, leadership quality, recognition of consumer rights and participating citizenship. -
(i) displayed by teacher is appreciation of nature.
(ii) The phenomenon involved in interface. -
(a) In charger and CD player etc., a very small dc supply is required and 220 V ac is converted to 6 V dc by using a rectifier. A rectifier is a device used to convert ac into dc.
(b) Values displayed by Mohan-scientific thinking and interest to learn more. -
(i) The main functions of a demodulator are:
(a) selecting the desired signal and rejecting the unwanted signals.
(b) demodulating the desired signal and amplifying it.
(c) displaying the original modulating signal in a desired manner.
(ii) All receivers like television and radio are demodulators.
(iii) In day to day life, demodulation is so common. An aeroplane, for example carries us to our destination town. we get off the plane and meet our loved ones. The carrier is to be left behind. In a demodulator, carrier wave is bypassed and only the original modulating signal is reproduced.
