#### 12th Standard Physics English Medium Reduced Syllabus Model Question paper - 2021 Part - 1

12th Standard

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Physics

Time : 02:45:00 Hrs
Total Marks : 70

Part I

Choose the most suitable answer from the given four alternatives and write the option code with the corresponding answer.

15 x 1 = 15
1. An uncharged metal sphere is placed between two equal and oppositely charged metal plates. The nature of lines of force will be

(a)

(b)

(c)

(d)

2. In three phase AC generator the three coils are fastened rigidly together and are displaced from each other by an angle

(a)

90°

(b)

180°

(c)

120°

(d)

360°

3. In an a.c. circuit with an inductor

(a)

voltage lags current by π/2

(b)

voltage and current are in phase

(c)

(d)

current lags voltage by π/2

4. In a LCR series a.c, circuit, the phase difference between current and voltage is 60°. If the net reactance of the circuit is 17.32Ω, the value of the resistance is

(a)

30Ω

(b)

17.32 Ω

(c)

10 Ω

(d)

1.732 Ω

5. Which of the following is used to study crystal structure?

(a)

microwave

(b)

infrared rays

(c)

ultraviolet rays

(d)

X-rays

6. Electromagnetic waves are _________ in nature .

(a)

parallel

(b)

transverse

(c)

longitudinal

(d)

Uni-directional

7. ________ radiations are used to study atomic structure.

(a)

UV

(b)

IR

(c)

X-rays

(d)

Gamma

8. The speed of light in an isotropic medium depends on,

(a)

its intensity

(b)

its wavelength

(c)

the nature of propagation

(d)

the motion of the source w.r.t medium

9. If γ is the frequency of characteristic X-ray line emitted by a target element of atomic number Z, then Moseley's law is

(a)

γ α Z

(b)

γ α $\sqrt Z$

(c)

γ α Z2

(d)

γ α Z3

10. The orbits in which electrons supposed to be revolving according to Rutherford are ___________

(a)

square-shaped

(b)

circular

(c)

rectangular

(d)

linear

11. __________ Scanning Electron Micrograph (SEM) showing the nano structures on the surface of a leaf from a lotus plant

(a)

Parrot fish

(b)

Morpho butterfly

(c)

Lotus leaf surface

(d)

Peacock feathers

12. From the follwoing semi-conductor devices _________ operates in forward bias only.

(a)

varactar diode

(b)

zener diode

(c)

light emitting diode

(d)

photo-diode

13. Noise is a form of __________ variation.

(a)

time

(b)

phase

(c)

amplitude

(d)

frequency

14. Atomic number of Si is ______

(a)

14

(b)

12

(c)

16

(d)

18

15. In a junction transistor the emitter region is heavily doped since emitter has to supply to the base Zener diode acts as a __________

(a)

minority carrier

(b)

majority carrier

(c)

acceptor ions

(d)

donor ions

16. Part II

Answer any 6 questions. Question no. 16 is compulsory.

6 x 2 = 12
17. (i) How is the speed of Electromagnetic waves in vacuum determined by the electric and magnetic fields? and
(ii) Do Electromagnetic waves carry energy and momentum?

18. When a wave undergoes reflection at a denser medium, what happens to its phase?

19. Give the results of Rutherford alpha scattering experiment.

20. Define atomic mass unit u.

21. What are sub atomic particles?

22. What kind of blueprint does the natural structure provide?

23. Part III

Answer any 6 questions. Question no.27 is compulsory.

6 x 3 = 18
24. Calculate the electric dipole moment for the following charge configurations.

25. How are the three different emfs generated in a three-phase AC generator? Show the graphical representation of these three emfs.

26. What is the phase relation between current and emf in an AC circuit containing a cpacitor only? Sketch a graph showing the variation the reactance of a capacitor with frequency.

27. Digine atomic mass unit. Find its energy equivalent in MeV

28. Write the application of nano robots in medical field?

29. Give the Schematic representation of valence band, conduction band, and forbidden energy gap. and draw energy band structure of
(a) Insulators
(b) Semiconductors
(c) Metals?

30. Part IV

5 x 5 = 25
31. Compute the speed of the electromagnetic wave in a medium if the amplitude of electric and magnetic fields are 3 × 104 NC-1 and 2 × 10-4 T, respectively.

32. The oscillating magnetic field in a plane Electromagnetic wave is given by
B = (8 x 10-6) sin (2 x 1011 t + 300 πx) T
(i) Calculate the λ of Electromagnetic wave.
(ii) Find the amplitude of electric field.

33. Explain the results of Rutherford α-particle scattering experiment.

34. Two stable isotopes of lithium $_{ 3 }^{ 6 }{ Li }$ and $_{ 3 }^{ 7 }{ Li }$ have respective abundances of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u respectively. Find the atomic mass of lithium.