CBSE 12th Standard Physics Subject Value Based Questions 5 Mark Questions 2021 Part - I
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CBSE 12th Standard Physics Subject Value Based Questions 5 Mark Questions 2021 Part - I
12th Standard CBSE
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Reg.No. :
Physics
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Shikhaj was working on a project for science exhibition. He considered a capacitance of 2\(\mu F\) having a capacity of operating under 1kV potential. When he reached to shop, he found that the shopkeeper is having a capacitors of 1 \(\mu F\) of 400 V rating. Shikhaj calculated minimum number of capacitances of 1 \(\mu F\) each, so he could arrange to form a capacitor of 2 \(\mu F\) .
Answer the following questions based on the above information:
(i) What are the calculations done by Shikhaj?
(ii) What do you think of Shikhaj? -
Ramaniamma was a childless window. She ran her life only by the pension for the Sr. citizens from the Government. When she switches ON one bulb in her house, all the other appliances get switched OFF. She could not even spend for an electrician. Sujatha living nearby decided to do something for her. She referred to Physics books and learned that the series combination for the household connection could be the reason. She called an electrician and had the circuit changed to parallel combination. The problem was solved and Ramaniamma was happy. She thanked Sujatha for her help to solve the problem.
Read the above passage and answer the following questions.
(i) What are the values possessed by Sujatha?
(ii) Why a parallel combination is used for household? Give two advantages. -
When a galvanometer of resistance G is shunted with a low resistance S, then the effective resistance \({ Re }_{ ff }\)of galvanometer becomes
\( { Re }_{ ff }=\frac { GS }{ G+S } \)
If the current is passed through such a galvanometer, then the major amount of current flows through the shunt and the rest through the galvanometer, then the major amount of current flows through the shunt and the rest through galvanometer., the current divides itself in the inverse ratio of resistances.
Read the above passage and answer the following questions:
(i) Why is the resistance of shunted galvanometer lower than that of a shunt?
(ii) A galvanometer of resistance.\(30\Omega \) What the fraction of the main current passes (i) through the galvanometer and (ii) through the galvanometer and (ii) through the shunt?
(iii) What are the basic values you learn from the above study? -
Aarushi wanted to perform an experiment of Faraday's law of electromagnetic induction. She told her father to bring some of the instruments such as a torch bulb, a coil and a bar magnet. She connected the bulb with the two terminals of the coil. And to check for induced emf, she moved the bar magnet back and forth near to the coil. The bulb started to glow. All her mother, father and elder brother surprised of this activity.
(i) What are the values displayed by Aarushi?
(ii) Give the Faraday's law of electromagnetic induction?
(iii) Write the equation to calculate induced emf of a coil of N number of turns? -
The number of electrical generators used in areas where small workshops exist created a lot of pollution. Kamal and his five friends did a survey and realised that like a multistoried building, a common generator could be set up for all these small workshops so that the noise and air pollution could be reduced. They had a tough time convincing the local bodies and now they are going to the NGO's and some financiers to help them to set up the generators.
Read the above passage and answer the following questions:
(i) What values did Kamal and his friends show>
(ii) Kamal peddles a stationary bicycle, the pedals of the bicycle are attached to a 100 turn coil of area 0.1m2. The coil rotates at half a revolution per second and it is placed in a uniform magnetic field of 0.01 T perpendicular to the axis of rotation of the coil. What is the maximum voltage generated in the coil? -
Shyam and his younger brother were at the restaurant. It was very clean there. None of the flies and insects were there. His younger brother asked him about the fluorescent UV lamp present at the corner. Shyam explained the functioning of UV lamp, how flies and insects get trapped by it?
(i) What are the values shown by Shyam?
(ii) Give the source of UV-rays.
(iii)Give the harmful effect of UV-rays. -
Kanchan while driving her scooty sees a woman behind driving a moped through his rear view mirror. She sees that her saree is almost touching the wheels of the vehicle. She stops her and alert that it may cause a severe accident.
Read the above passage and answer the folllowing questions:
(i) What values do you observe in Kanchan?
(ii) Name the mirror used in rear view in scooty. Draw a ray diagram for the same. -
"Know your face beauty through comp[lexion meter" was one of the stall on science exhibition. A student interested to know his/her face beauty was made to stand on a platform and light from a lamp was made to fall on his/her face. The reading of complexion meter indicated the face beauty of the student which might be very fair, fair,semi-fair, semidark dark etc.
(i) What is the basic concept used in the working of complexion meter?
(ii) How is the face beauty recorded by face complexation meter?
(iii) What basic values do you learn from the above study? -
Natural radioactivity is a spontaneous and self disruptive activity exhibited by a number of heavy elements in nature. Thus a heavy element disintegrates by itself without being forced by any external agent to do so.
According to radioactive decay law, the number of atoms disintegrated per second (i.e., rate of disintegration of radioactive atoms) at any instant is directly proportional to the number of radioactive atoms actually present in the sample at that instant, i.e., \(-\frac { dN }{ dt } \propto N \ or \ R=-\frac { dN }{ dt } =\lambda N,\) where is \(\lambda \) decay constant.
Read the above passage and answer the following questions :
(i) The count rate from a radioactive sample containing \({ 10 }^{ 16 }\) atoms is \(4\times { 10 }^{ 16 }\) per second. What is the value of decay constant?
(ii) Name the three types of radiactive radiations. Which one of them is most penetrating?
(iii) What does radioactive decay law imply in day to day life? -
Ajeet's younger brother was just seeing class 12th books. He wondered to know the structure of atoms and arrangement of electrons and protons in them. As he was a class 6th student, he did not understand the whole concept of atomic structure. Ajeet helped him to understand the structure of atoms.
Read the above passage and answer the following questions:
(i) What are the values shown by Ajeet?
(ii) On which metal Rutherford performed \(\alpha \) - particles scattering experiment?
(iii) How Rutherford concluded that at the centre of atom there is massive nucleus which contains positive charge? -
Einstein was the first to establish the equivalence between mass energy. According to him, whenever a certain mass \(\left( \Delta m \right) \) disappears in some process, the amount of energy released is \(E=\left( \Delta m \right) { c }^{ 2 },\) where c is velocity of light vacuum \(\left( =3\times { 10 }^{ 8 }m/s \right) .\) The reverse is also true, i.e., whenever energy E disappears, an equivalent mass \(\left( \Delta m \right) ={ E/c }^{ 2 }\) appears.
Read the above passage and answer the following questions :
(i) What is the energy released when 1 a.m.u. of mass disappears in a nuclear reaction?
(ii) Do you know any phenomenon in which energy materialises?
(iii) What values of life do you learn from this famous relation? -
Marie Curie and her teacher turned husband Pierre Curie worked hard to extract radium chloride (RaCl2) from uranium ore. They succeeded in 192 after a long struggle. About 0.19 g of RaCl2 was extracted and its radioactivity was studied. They were awarded by the noble prize, which they shared it which they shared it which they shared it with Henri Becquerel.
Read the above passage and answer following questions:
(i) What are the values shown by Marie Curie and her husband?
(ii) What do you understand by radioactivity? How the half-life period is related to the disintegration constant?
(iii) How is average-life of radioactive element related to half-life? -
\(p-n\) junction is a semiconductor diode.It is obtained by bringing \(p-\) type semiconductor include contact with \(n-\) type semiconductor. A thin layer is developed at the \(p-\) junction which is devoid of any charge carrier but has immobile ions. It is called depletion layer. At the junction a potential barrier appears, which does not allow the movement of majority charge carriers across the junction in the absence of any biasing of the junction.
\(p-\)n junction offers low resistance when forward biased and high resistance when reverse biased. Read the above paragraph and answer the following questions:
(i) Can we measure the potential barrier of \(p-n\) junction by putting a sensitive voltmeter across its terminals?
(ii) What practical lesson do you draw from the above study? -
Shorya usually enjoyed loud music. One day his music system was not producing very loud sound. Shorya gets disappointed. He discussed his problem with his big brother Kamal. Kamal advised him to connect an amplifier in series with the amplifier of the stereo system. This increased the sound of Shroya's music system considerably. Read the above passage and answer the following questions:
(i) Which value is displayed by Kamal?
(ii) Why the loudness of music system get increased on connecting amplifier?
(iii) Give the equation for current gain in the transistor as an amplifier. -
In the famous conversation, Rakesh Sharma, the first Indian Astronaut in space, was asked by the Prime Minister Indira Gandhi as to how India looked from space.To which he replied,'Sare Jahan Se Achcha' (better than the whole world).
Read the above passage and answer the following questions:
(i) Which scientific mode of communication enabled the Prime Minister to speak to the Astronaut?
(ii) Name the scientific values displayed in this anecdote.
(iii) Which values are being reflected in the reply given by the astronaut?
(iv) Give one more example of this scientific mode of communication in everyday life situations.
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CBSE 12th Standard Physics Subject Value Based Questions 5 Mark Questions 2021 Part - I Answer Keys
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(i) Total potential difference across each row = 1000 V
Potential difference across each capacitor = 400 V
Number of capacitors in series,
\(n=\frac { 1000 }{ 400 } =2.5\ \approx \ 3\)
Capacitance of capacitors in series, Cs = \(\frac { 1 }{ 3 } \mu F\)
Let m be rows of capacitors, for an equivalent capacitance of \(2\mu F\), we have
\(m\times \frac { 1 }{ 3 } =2\Rightarrow m=6\)
Hence, total number of capacitance required
= m x n = 6 x 3 = 18
Total 6 rows of capacitor in parallel with three capacitors in each row.
(ii) We think that Shikhaj knows the value of money and have the ability to calculate scientifically in daily life. -
(i) Care for elderly people, empathy, willingness to gain knowledge.
(ii) A parallel circuit can run several devices using the full voltage.
The two advantages are as follows:
(a) If one appliance fails, then others can run normally.
(b) If one of the device shorts, the other devices will receive no voltage preventing overload damage. -
(i) The shunt is a low resistance connected in parallel with the galvanometer. Therefore, the combined resistance is less than that of the shunt.
(ii) Let I be the total current passing through the shunt galvanometer. Let \({ I }_{ g }\),\({ I }_{ s }\) be the currents through galvanometer of resistances G and shunt of resistance S respectively. As current divides itself in the inverse ratio of the resistances, therefore, fraction of current passing through galvanometer
= \(\frac { { I }_{ g } }{ I } =\frac { S }{ G+S } =\frac { 3 }{ 30+3 } =\frac { 1 }{ 11 }\)
\(Fraction \ of \ current \ passing \ through \ shunt=\frac { { I }_{ s } }{ I } =\frac { G }{ G+S } =\frac { 30 }{ 30+3 } =\frac { 10 }{ 11 } \\ \)
(iii) From the above study, we find that the current always divides itself in the inverse ratio of resistances. The major part of current flows through the shunt, which is the path of low resistance. Similarly in life, if different paths are available to reach a destination, then one selects a path of least resistance to reach there. This would save both, time and energy. -
(i) Aarushi is an intelligent girl. She is innovative and has good command over physics.
(ii) The two laws of Faraday are given below;
(a) An emf is induced, when magnetic flux linked with the coil changes.
(b) The induced emf is directly proportional to the rate of change of magnetic flux.
(iii) For N number of turns in a coil, induced emf is given by
e = - N \(\cfrac { d\phi }{ dt } \) [ \(\because \cfrac { d\phi }{ dt } \) = rate of change of magnetic flux] -
(i) Kamal and his friends show the values of concern to the environments, Team spirit and managing responsibilities.
(ii) Here, v = 0.5 Hz, N = 100, A = 0.1m2 and B = 0.01T
We know that induced emf, \({ \varepsilon }_{ 0 }\) = NBA (2\(\pi \) v)
= 100 \(\times\) 0.01 \(\times\) 0.1\(\times\) 2 \(\times\)3.14\(\times\) 0.5 = 0.314 V
The maximum voltage is 0.314V.
We urge you to explore such alternative possibilities for power generation. -
(i) Shyam is intelligent and has clarity in explaining facts.He also aware about health.
(ii) UV-rays are produced by the sun and is trapped by ozone layer.
(iii) UV-rays can cause skin cancer, so it is carcinogenic. -
(i) The values we observe in Kanchan are as follows:
(a) Concern about others
(b) Observation of traffic rules
(c) Resposible citizen
(ii) Convex mirror is used in rear viwe in scooties. The ray diagram for convex mirror is
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(i) The basic concept used in the working of complexation meter is a photoelectric effect.
(ii) The reading of complexation meter depends on the current generated from the light reflected from the face. Fairer the colour more is the light reflected and vice versa.
(iii) Complexation meters judge your beauty only. The inner beauty of a person is judged by the virtues he or she posseses. In my opinion, inner beauty is much more valuable than the face beauty. -
(i) Here, \(N={ 10 }^{ 16 } \ and \ \frac { dN }{ dt } =4\times { 10 }^{ 16 } \ per \ sec.\lambda =?\)
\(From \ \frac { dN }{ dt } =\lambda N\)
\( \lambda =\frac { dN/dt }{ dt } =\frac { 4\times { 10 }^{ 16 } }{ { 10 }^{ 16 } } =4\times { 10 }^{ 16 }{ sec }^{ -1 }\)
(ii) The three types of radiactive are radiations are : \(\alpha \)-rays; \(\beta \)-rays and \(\gamma \)-rays. Out of then, \(\alpha \)-rays have maximum penetrating power.
(ii) Radioactive decay law is the law of mass action, i.e., larger the available mass, greater is its rate of decay. The same applies in day to day life. Larger the population, greater is their decay rate, i.e., death rate, i.e., under given conditions, when number of people is large, the rate at which they die is also large. The reverse is also true. -
(i) Ajeet is intelligent, cooperative and has good command over Physics.
(ii) Rutherford used gold foil of 10-8m thickness.
(iii) When Rutherford was performing \(\alpha \) - particles scattering experiment, he observed that very less number of \(\alpha \) - particles retrace their path. Thus, he concluded that there is a positive massive part at the centre of atom and named it nucleus. -
(i) Here, \(\Delta m=1\quad a.m.u.=1.66\times { 10 }^{ -27 }kg\)
\(E=\left( \Delta m \right) { c }^{ 2 }=1.66\times { 10 }^{ -27 }{ \left( 3\times { 10 }^{ 8 } \right) }^{ 2 }=1.49\times { 10 }^{ -10 }J\)
(ii) Yes, in the phenomenon of pair production. Under suitable conditions, a photon materialises into an electron and a position : \(\gamma ={ e }^{ -1 }+{ e }^{ +1 }\)
(iii) Einstein's relation, \(E=\left( \Delta m \right) { c }^{ 2 }\) emphasis that when certain mass disappears, an equivalent amount of energy appears. The reverse is also true. It Implies that to gain something, you have to lose another in equivalent amount. No one can have all gains together or all losses together. It also implies that nothing come for free. You have to pay the price in one form and acquire something in the desired form. -
(i) Values shown here are dedication, hard working nature, brilliance, true justification of the help when helped by another, honesty and gratitude.
(ii) The phenomenon of spontaneous emission of \(\alpha \) , \(\beta \) and \(\gamma \)-particles by the nuclide is known as radioactivity. Half-life period is related with the disintegration constant as,
\({ T }_{ 1/2 }=\frac { 0.693 }{ \lambda } \)
(iii) Average life of radioactive element,
\(\tau ={ 1.44T }_{ 1/2 }\) -
(i) We cannot measure the potential barrier of \(p-n\) junction by putting a sensitive voltmeter across its terminals because there are no free electrons or holes in the depletion layer. And in the absence of forward biasing, the depletion layer offers infinite resistance.
(ii) From the above study,we find that when some move supports the tendency of majority of the people, the resistance/(opposition) is lowered and output current (desired result) is large (appreciable) However, when some move is against the tendency of majority of people, it suffers rough weather. -
(i) Kamal is caring for his younger brother. He is an intelligent boy.
(ii) On connecting two amplifiers in series, its amplification gain gets multiplied. Hence, the loudness of music system increases.
(iii) Current gain in the transistor as an amplifier is given by
\({ \beta }_{ AC }=\frac { \triangle { I }_{ C } }{ \triangle { I }_{ B } } \)
where \(\triangle { I }_{ C }\) = change in collector current
\(\triangle { I }_{ B }\) = change in base current. -
(i) Radio wave communication system.
(ii) Use of scientific and technological advancement in service to mankind.
(iii) Patriotism and love for the country, presence of mind.
(iv) Television communication system.
