Subject

Physics

Class

CBSE Class 12

Pre Boards

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Sample Papers

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 Multiple Choice QuestionsShort Answer Type

11.

A circular coil of cross-sectional area 200 cm2 and 20 turns is rotated about the vertical diameter with angular speed of 50 rad s−1 in a uniform magnetic field of magnitude 3.0 × 10−2T. Calculate the maximum value of the current in the coil.

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12.

A wire whose cross-sectional area is increasing linearly from its one end to the other, is connected across a battery of V volts.
Which of the following quantities remain constant in the wire?
(a) drift speed
(b) current density
(c) electric current
(d) electric field

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13.

Name the junction diode whose I-V characteristics are drawn below

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14.

Define the distance of closest approach. A α-particle of kinetic energy 'K' is bombarded on a thin gold foil. The distance of the closest approach is 'r'. What will be the distance of closest approach for a α-particle of double the kinetic energy?   

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15.

Write two important limitations of Rutherford nuclear model of the atom.

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16. Find out the wavelength of the electron orbiting in the ground state of the hydrogen atom.


Radius of ground state of hydrogen atom =0.53A°  = 0.53 x10-10m
According to de Broglie relation 2πr = nλ
For ground state n=1
2 x 3.14 x 0.53 x 10-10= 1 x λ
therefore, λ = 3.32 x10-10 m
= 3.32 A° 

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17. Define the magnifying power of a compound microscope when the final image is formed at infinity. Why must both the objective and the eyepiece of a compound microscope has short focal lengths? Explain.
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18.

Which basic mode of communication is used in satellite communication? What type of wave propagation is used in this mode? Write, giving a reason, the frequency range used in this mode of propagation.

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19. Write the two processes that take place in the formation of a p-n junction. Explain with the help of a diagram, the formation of the depletion region and barrier potential in a p-n junction.  
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20.

(i) Obtain the expression for the cyclotron frequency.
(ii) A deuteron and a proton are accelerated by the cyclotron. Can both be accelerated with the same oscillator frequency? Give reason to justify your answer.

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