Subject

Physics

Class

CBSE Class 12

Pre Boards

Practice to excel and get familiar with the paper pattern and the type of questions. Check you answers with answer keys provided.

Sample Papers

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 Multiple Choice QuestionsShort Answer Type

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11.

A rectangular conductor LMNO is placed in a uniform magnetic field of 0.5 T. The field is directed perpendicular to the plane of the conductor. When the arm MN of length of 20 cm is moved towards left with a velocity of 10 ms–1, calculate the emf induced in the arm. Given the resistance of the arm to be 5 (assuming that other arms are of negligible resistance) find the value of the current in the arm.


Emf induced in a moving rod is given by, 

E = -Blv

Emf induced in a moving rod is given by, 

E = + Blv

   = 0.5 x 0.2 x 10

   = 1 v

Therefore, current in the rod is given by, 

I =  

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12.

A wheel with 8 metallic spokes each 50 cm long is rotated with a speed of 120 rev/min in a plane normal to the horizontal component of the Earth’s magnetic field. The Earth’s magnetic field at the plane is 0.4 G and the angle of dip is 60°. Calculate the emf induced between the axle and the rim of the wheel. How will the value of emf be affected if the number of spokes were increased?

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13.

Define the current sensitivity of a galvanometer. Write its S.I. unit. Figure shows two circuits each having a galvanometer and a battery of 3 V. When the galvanometers in each arrangement do not show any deflection, obtain the ratio R1 / R2

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14.

A wire AB is carrying a steady current of 12 A and is lying on the table. Another wire CD carrying 5A is held directly above AB at a height of 1 mm. Find the mass per unit length of the wire CD so that it remains suspended at its position when left free. Give the direction of the current flowing in CD with respect to that in AB.
[Take the value of g = 10 ms–2]

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15.

The graph shown in the figure represents a plot of current versus voltage for a given semiconductor.

  

Identify the region, if any, over which the semiconductor has a negative resistance.

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16.

Define the activity of a given radioactive substance. Write its S.I. unit.          

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17.

Write the expression for the de Broglie wavelength associated with a charged particle having charge ‘q’ and mass ‘m’, when it is accelerated by a potential V.

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18.

Draw typical output characteristics of an n-p-n transistor in CE configuration. Show how these characteristics can be used to determine output resistance.        

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19.

A parallel beam of light of 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1 m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre of the screen. Calculate the width of the slit.

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20.

A convex lens of focal length f1 is kept in contact with a concave lens of focal length f2. Find the focal length of the combination.

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