06 “The three great essentials to achieve anythingworth while are: Hard work, Stick-to-itiveness,

and Common sense.” Thomas A. Edison PRACTICE PAPER

SECTION -AQ.1 What is the shape of the wave front on earthfor sunlight?

Q.2 Name the electromagnetic radiation usedfor viewing objects through haze and fog.

Q.3 Two wires of equal length, one of copperand other of manganin have the same resist-ance. Which wire is thicker?

Q.4 Name the physical quantity that has a unitof Weber / ampere.

Q.5 Draw a graph showing the dependence ofintensity of transmitted light on the anglebetween polarizer and analyzer.

SECTION -B Q.6 A variable frequency AC source is connect-ed to a capacitor. How will the displacementcurrent change with decrease in frequency?

Q.7 Three photo diodes D1, D2 and D3 are madeof semiconductors having band gaps of 2.5eV,2eV and 3eV, respectively. Which ones will beable to detect light of wavelength 6000 A0?

Q.8 Draw the graph showing the variation ofbinding energy per nucleon with mass numberof different nuclei. Mark the region where thenuclei are most stable.

Q.9 Two point charges +q and +4q are separatedby a distance of 6a. Find the point on the linejoining the two charges where the electric fieldis zero.

Q.10 An accumulator is connected first to anexternal resistance R1 and then to anotherexternal resistance R2 for the same time. Atwhat value of the internal resistance of theaccumulator will the amount of heat dissipatedin the external resistances be the same in thetwo cases?

Q.11 (a)What will be the output wave form if thegiven inputs are fed to an AND gate?

(b) Write the truth table of AND gate?

Q.12On the figure shown, find out the currentpassing through RL and Zener diode.

SECTION -C

Q.13 State Gauss's theorem in electrostatics.Apply this to show that for a spherical shell,the electric field inside a spherical shellvanishes, whereas outside it is as though allthe charge had been concentrated at theorigin

Q.14 Distinguish between the terms reac-tance and impedance of an AC circuit. Provethat an ideal capacitor connected to an ACsource does not consume any power.

Q.15A network of four capacitors each of15µF capacitance is connected to a 500 Vsupply as shown in the figure. Determine (a)equivalent capacitance of the network and(b) charge on each capacitor.

Q.16

Q.17 Define the terms threshold frequency andstopping potential for photoelectric effect. Showgraphically how the stopping potential for agiven metal varies with frequency of incidentradiation. Mark threshold frequency in thisgraph.

Q.18 A galvanometer with a coil of resistance 15shows full scale deflection for a current of 45 mA.How will you convert the galvanometer into (i)An ammeter of range 0 to 5 A (b) A voltmeter of range 0 to 10 V

Q.19 State Huygen's principle and prove laws ofrefraction based on this.

Q.20 In a Young's double slit experiment; asource of wavelength 6000A0 is used. The screenis placed 1 m from the slits. Fringes, formed onthe screen are observed by a student sitting closeto the slits. The student's eye can distinguish two

neighbouring fringes. If they subtend an anglemore than 1 minute of arc, calculate the maxi-mum distance between the slits so that thefringes are clearly visible. Using this informa-tion calculate the position of 3rd bright and 5thdark fringe from the centre of the screen.

Q.21 The sequence of stepwise decay of radioac-tive nucleus is

SECTION -D

If the nucleon number and atomic number forD2 are respectively 176 and 71, what are the cor-responding values for D and D4 nuclei? Justifyyour answer.

Q.22 If the average life time of an excited state ofhydrogen atom is of the order of 10-8 s, estimatehow many orbits an electron makes when it is instate n= 2 and before it suffers a transition tostate n = 1?

Q.23 What is meant by rectification? Explain afull wave rectifier with a neat labelled diagram.

Q.24 Draw a schematic diagram showing the (i)ground wave (ii) sky wave and (iii) space wavepropagation modes for em waves.

Write the frequency range for each of the fol-lowing:(i) Standard AM broadcast (ii) Television(iii) Satellite communication

Q.25 (a) Derive Lens maker's equation. (b) (i) If f = 0.5 m for a glass lens, what is the pow-er of the lens? (ii) The radii of curvature of thefaces of a double convex lens are 10 cm and 15 cm.Its focal length is 12 cm. What is the refractive in-dex of glass? (iii) A convex lens has 20 cm focallength in air. What is focal length in water? (Re-fractive index of air-water = 1.33, refractive indexfor air-glass = 1.5.)

Q.26 i) Using Biot and Savart's law, derive an ex-pression for the magnetic field Intensity at thecentre of a current carrying circular coil. (ii)A coil of N turns and radius R carries a currentI. It is rewound to make another coil of double thenumber of turns. Calculate the ratio of the mag-netic moments of the new coil and the original coil.

These questions and the marks alongside aremeant for practice purpose only. Students areadvised to check format, syllabus and marks

for Board test papers with their teachers.Questions have been given by teachers and NIE

is not responsible for them.

CHECK YOUR SCORE IN PHYSICSGayathri S V, PGT Physics, Kendriya Vidyalaya SAP, Thiruvananthapuram, offers you a practice paper to see where you stand in the subject

EXAMS sound terrifying,right? Studying for theboard exams was the most

stressful thing I have gonethrough. Constantly being toldby seniors, teachers, friends andfamily, that it is going to be toughadded to the anxiety and stress.Indeed, it was a tough one butinstead of being influenced byothers' perspectives, I chose togo by my opinion. Soon, I founda different approach and it allseemed like a cakewalk. I or-ganised myself and put the timeI had, to effective use. I priori-tised according to my comfortzone. The month in which I ap-peared for the boards went bysmoothly, without any trace oftension. Just like any other per-son would say, I urge everyonetaking their board exams thisyear to have an eagle-eye duringtheir preparation, show utmostdedication and not think of re-sorting to shortcuts.

As the academic year beginsfor a majority of students, hereare some tips to ease you up.

1Start off today and ward offthe thought of procrastina-

tion completely.

2Prepare your schedule andorganise yourself.

3Write down your notes foreach chapter and summarise

them in your own words.

4Accept every subject as it is.

5See your subjects merely assubjects, not as a burden. In

topics like history, it makes senseto create timelines and notedown the dates for specificevents along with the names inorder to remember them longer.

6Do not bogged down by thesyllabus. In science topics it

is better to thoroughly learn thetheory and then complementthat with practical knowledgein order to remember the con-cepts better.

7Never categorise your sub-jects according to your 'likes'

or 'dislikes'.

8Enumerate your prioritylist based on parameters

like tough, moderate or easy.

9Allott time for as many revi-sions as you feel you require.

10Assimilate confidence.

Sounds easy? These 10points are the mantras that youshould start chanting and prac-tising immediately.

Wishing you all a smoothboard examination!ARAVIND SRIVATSA, MES KKPS,Bengaluru

Ready, Steady and just STUDY!

P R A C T I C E P A P E RPHYSICS

CLASS XII, CBSE

All questions are compulsory. Questions 1 to 5 are very short answertype questions and carry one mark each. Questions 6 to 12 carry two marks each,questions 13 to 24 carry three marks eachand questions 25 to 27 carry five marks each. There is no overall choice. However, aninternal choice has been provided. Use of calculators is not permitted. How-ever, you may use log tables if necessary. You may use the following values of physical constants wherever necessary.

GENERAL INSTRUCTIONS

Dealing with distraction isnot easy and my challengewas procrastination and

lack of concen-tration duringstudies. Usually,people say thatthey get distract-ed due to theirmobile phones orsocial networking

sites, but in my case, it's com-pletely different as I feel that thelack of interest, concentrationor dedication is overtaking mystudy goals. I believe that if youare completely dedicated towardssomething there is no such thingthat can force you to change yourplans.

To subjugate this, medi-tation is the best option that I pre-

fer. In mindfulness meditation,we learn how to pay attention toour breath – as we inhale and ex-hale, and notice when the mindwanders from this task. Thispractice of returning to thebreath builds the muscles of at-tention and mindfulness. Whenwe pay attention to our breath,we learn how to return to, andremain in, the present moment– to anchor ourselves in the hereand now on purpose, withoutjudgment. I get a lot of benefitsfrom it. Peace of mind, good sus-tainability and health, concen-tration and attention are someof the major outcomes of it.

UDISHA TIWARI, class IX, City

Montessori School, Gomtinagar

Extension, Lucknow

Meditate to improve concentration!