I Series SOS I Roll No. m-r ;f.

Code No. 55/1 m;f.

Candidates must write the Code on the title page of the answer-book.

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Please check that this question paper contains 15 printed pages. Code number given on the right hand side of the question paper should be

written on the title page of the answer-book by the candidate. Please check that this question paper contains 30 questions. Please write down the Serial Number of the question before

attempting it.

15 minutes time has been allotted to read this question paper. The question paper will be distributed at 10.15 a.m. From 10.15 a.m. to 10.30 a.m., the students will read the question paper only and will not write any answer on the answer script during this period.

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Time allowed : 3 hours

55/1

PHYSICS (Theory) mfdd5 fa$1191 (f};~nPtid5)

1

I

Maximum Marks: 70

31(~ 3/q; : 70

P.T.O.

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(v) Use of calculators is not permitted. However, you may use log table{} if nece33ary.

(vi) You may use the following values of physical constants wherever necessary :

c = 3 x 108 m/s

h = 6q3 x I0- 34 Js e = 16 X Io-19 c J..l0 = 4rr x Io-7 TmA-1

_I_ = 9 X 109 N m2 c-2 4m~

0

me = 91 x I0-31 kg

"ffT1TP.1 ~ :

55/1

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3Jk JRitq; 7!,1E 3fq; q;r '# I (iii) JfFf 9 fr 18 ff JRitq; JfFf c:T 3fq; q;r '#, JfFf 19 fr 27 ff JRitq; JfFf rfR 3fq;

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2

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(v) c11HjJH2~ it Mrr qff 31pTFrr ;rp # I ~ ~ 31/q~2fCh if fit 31TV C19,'10/Chl2f ~ CfiT Jl"lit7r Chr ~ ! I

(vi) ~ 3ffCT RARIRsm 'J:ffFrrq; R2fdiChJ" it 11frif Cfi! mrr cnr ~ ! :

c = 3 x 108 m/s

h = 663 x 1o-34 Js ,~~ e = 16 x 10-19 C

Jl0 = 41t x l0-7 T m A-1

-

1- = 9 X 109 Nm2 c-2

41tE 0

me= 91 x 10-31 kg

1. Define electric dipole moment. Write its S.I. unit.

2. Where on the surface of Earth is the angle of dip 90 ?

3. A hollow metal sphere of radius 5 em is charged such that the potential on its surface is 10 V. What is the potential at the centre of

1

1

the sphere ? 1

~ ~ 5 em~~~~~ cit w-IT~ fcfiGfT ~ ~ fqj ~ ~ I

C1iT fcrqq 10 v -m ~ ~ 1 ~ ~ ~ ~ 1R. fcrqq ~ m-rn ?

4. How are radio waves produced ? 1

5. Write any two characteristic properties of nuclear force. 1

55/1 3 P.T.O.

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6. Two bar magnets are quickly moved towards a metallic loop connected across a capacitor 'C' as shown in the figure. Predict the polarity of the capacitor. ' 1

m -q ~ ~ ~ -GT ~ ~ Cfil, ~ ifi ~ ~ 11m

0. Plot a graph showing the variation of coulomb force (F) versus _ (r~} where r is the distance between the two charges of each pa1r of charges : (1 J.1C, 2 J.1C) and (2 J.tC, - 3 J.1C). Interpret the graphs obtained.

~ ~ ~ ~. (1 J.1C, 2 J.1C) am (2 J.1C, -3 J.1C) ~ ft;m: ~ ~ (Fl cnr (r~) ~ W-T ~ ~ ~ ft;m: ~ (mtfi)~ I -ey;n: m ~ ~ ~ ~ ~ aftTi q,l ~ r ~ I >rll{f ~ (ft) q,l ~ ~ I

1. Write the expression for Lorentz magnetic force on a particle of charge 'q' moving with velocity 1 in a magnetic field B. Show that

2

no work is done by this force on the charged particle. 2

OR

A steady current (11) flows through a long straight wire. Another wire carrying steady current (12) in the same direction is kept close and parallel to the first wire. Show with the help of a diagram how the magnetic field due to the current 11 exerts a magnetic force on the second wire. Write the expression for this force.

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6.

13. What is sky wave communication ? Wh:y is this mode of propagation restricted to the frequencies only upto few MHz ?

14.

~-m ~ -B rCtiR ~ ifi qf{qS!(lll f.:lcm CfiT Olll qcfilCfi{U I fcfi

)5/1

fet capacitance of three identical capacitors in series is 1

J..lF. What

rill be their net capacitance if connected in parallel ?

i'ind the ratio of energy stored in the two configurations i

f they are

>oth connected to the same source.

2

m ~ c~-mn ~~ ~ ~ ~ ~

~ ~ c~) ~ ~ m ~. ~ ~ c~ ~) J tR w:rr 'l'IT, ~ AJ = z.. (i) R ~X~ l1Rt cf ~ ~ ~ aw:ffi ~ ~ fGGrr l17-ll, m ~ ~ cnl~~~irfr? (ii) fTl

20. Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies, v1 > v2, of incident radiation having the same intensity. In which case will the stopping potential be higher ? Justify your answer. 3

. m ~ am v1 ~ v2 ~ ( v1 > v2) t ?J ~ Mfctl

23. Draw a labelled diagram of a full wave rectifier circuit. State its working principle. Show the input-output waveforms. 3

~ "&rr f~t:!CfliU ~ ctiT ~ 'iiGifCfl(i ~ ~ ~ , Cfli4CfliU ~ ~ I mm 3ffi ~ m-~ it ~ I

24. (a) Using de Broglie's hypothesis, explain with the help of a suitable diagram, Bohr's second postulate of quantization of energy levels in a hydrogen atom.

(b) The ground state energy of hydrogen atom is - 136 eV. What are the kinetic and potential energies of the electron in this state ? 3

(a) ~ ~ Cb1 4RCfl(."Rftqj ~

A 1--------.X

z.

B y

10

3

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26. A compound microscope uses an objective lens of focal length 4 em and eyepiece lens of focal length 10 em. An object is placed at 6 em from the objective lens. Calculate the magnifying power of the compound microscope. Also calculate the length of the microscope.

OR

A giant refracting telescope at an observatory has an objective lens of focal length 15 m. If an eyepiece lens of focal length 10 em is used, find the angular magnification of the telescope.

If this telescope is used to view the moon, what is the diameter of the image of the moon formed by the objective lens ? The diameter of the

3

moon is 342 x 106 m and the radius of the lunar orbit is 38 x 108 m. 3

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~ ~ ll ~ fcmffi "Wffif ~ ~ ~ ~ cn1 ~ ~ 15 m ~ I ~ ~ 10 em~ ~ cnl ~ ~ CiiT ~ ~ ~' m ~ ~ Cfif~~~~?

~~~it %11f ~ ~ ~. -m ~ ~ ~ ~ -aR ~ ~ 51f('1~kj CfiT "&1m ~ ~ ? ~ CfiT "&1m 342 X 106 m ~ am ~ cnl ~ cnl ~ 38 x 108 m ~ I

55/1 1 1 P.T.O.

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27. Two heating elements of resistances R1 and R2 when operated at a constant supply of voltage, V, consume powers P1 and P2 respectively. Deduce the expressions for the power of their combination when they are, in turn, connected in (i) series and (ii) parallel across the same voltage supply. 3

R1

~ R2

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(c) Ra m~ ~ fcfim ~1~

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