12 nvla physics ii

8/2/2019 12 Nvla Physics II

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SECOND TERMINAL EXAMINATION-2011

ANSWER KEY- PHYSICS II

Q. No Scoring IndicatorsSplit

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1 a) Statement of coulombs law of electrostatics 1

b) No. The least charge is 1.6 x 10-19 C. Explanation of Quantization

of electric charge ( Q = ne) 1

c)

The forces excerted by the charges 5micro coulomb on C are equal and

is given by NFF BA 09.05

105105109 669=

==

These are resolved by vertical and horizondal components. Vertical are

cancel out.

Total force = NFFF ABA 161.0

5

209.02cos2coscos ===+

along CX 2 4

2 a)

R=10+6.6+10=26.6W 2

b) Total resistance = 1.6 + 3.4 = 5 ohm

I = V/ R = 5 / 5 = 1 A and V = IR = 1 x 1.6 = 1.6 v 2 4

3 a) Statement of Biot - Savart law 1

b) Derivation 2 3

4 a) Declination , dip and horizontal component of earths

magnetic field and its explanation 3

b) Explanation of dia , para and ferromagnetic substances 2

c) Sodium. ( Sodium is Para magnetic and the remaining all are diamagnetic ) 1 6

B(5mc)

B`

A`

Xqq

q q

A(5mc)

5 m

5 m

C2m

10W 10W

10W

10W

10W

10W 10W

10W10W 10W


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5 a) Explanation of eddy current 1

b) In speedometer, a small magnet rotates in an aluminum drum and

produces a magnetic field. Rotating magnet produces eddy current in

the drum, drum turns in the direction of rotating field.

A pointer attached to the drum indicates the speed 1 2

6 a) Explanation of Watt less current 2

b) Phasor diagram of LCR and derivation of power 3

c) E = - L dI / dt = -2 x 10 -3 x -1 / 10 -3 = 2V 1 6

7 Davison Germer experiment wave nature l= h / mv

Twinkling of stars Refraction = sin I / sin r

Alpha particle experiment distance of closest approach Rutherford

Blue colour of the sky Scattering Rayleigh 8 X 1/2

4

8 (a) UV ray (b) microwaves (c) Infrared (d) visible light 4 X 1/2

2

9 a) Ray diagram + Explanation 2

b) Explanation least distance distinct vision 1 3

10 a) Explanation coherent sources 1

b) No. The phase of waves emitted from them will be changing independent

of each other. Hence the phase difference between two independent

sources cannot be constant with time. 1

c) Derivation of band width 2

d) I1 /

I2

= (a1/ a

2)2 = 81 / 1 , a

1: a

2= 9 ; 1

a1= 9a

2

Imax

/ Imin

= (a1

+ a2

)2 /(a1

- a2

)2 = ( 9a2

+ a2

)2 / ( 9a2

- a2

)2 = 25 / 16 2 6

11 a) Diagram + Derivation 3

b) I1= 0 , r

1= 0 n = 1.52 and i

2= 90

n = sin i2/ sinr

2

r2= 4108 and A = r

1+ r

2= 0 + 4108=4108 2 5

ll


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12 a) Statement 4 X 1/2

b) Derivation 2

c) Threshold wavelength = hc / 0

=6.62 x 10-34 x 3 x 108 / 4.4 x 1.6 x 10-19 = 2821A0

The wavelength of light is greater than threshold wavelength and

it cannot eject electrons from copper 2 6

13 a) N / N0= (1/2) t/T

N / N0= (1/2) 25/12.5 = (1/2) 2 = 1/4 2 2

14 a) Postulates 2

b) Explanation + formula 2

c) Energy level diagram 2 6

12 nvla physics ii

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