With the help of a labelled diagram, obtain an expression for th

Subject

Physics

Class

ICSE Class 12

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 Multiple Choice QuestionsShort Answer Type

41.

A sinusoidal voltage e = e0 Sin (wt) is fed to a common emitter amplifier. Draw neatly labelled diagrams to show:

(i) Signal voltage

(ii) Output voltage of the amplifier.

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42. Make a truth table showing inputs at A and B and outputs at X, Y and Z for the combination of gates shown in figure below:


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 Multiple Choice QuestionsLong Answer Type

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43. With the help of a labelled diagram, obtain an expression for the electric field intensity ‘E’ at a point P in broad side position (i.e., equatorial plane) of an electric dipole. 


Electric field intensity at a point on the broad side-on position equatorial line: Consider an electric dipole consisting of two equal but opposite charges -q and +q separated by a vector distance 2l. Let P be a point at a distance r from the centre of the dipole O. The electric intensity at P due to the dipole is the vector sum of the field due to the charge -q at A and +q at B.


Electric intensity at P due to - q = EA

But    AP2 = r2 +l2;    

where AO = OB = l

Magnitude of EA is |EA| = 







The resultant intensity is the vector sum of.

EA and EB can be resolved into two components.

The y-components of the fields cancel each other because E
A sin θ = EB sin θ and they are oppositely directed. The x-components add up to give the resultant field E.



From the above two equations for Eeq and Eaxial we find that the electric intensity at an axial point is twice the electric intensity at a point on the equatorial position, lying at the same distance from the centre of the dipole.
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44. What is meant by ‘Chromatic aberration’? A thin convex lens of focal length 30 cm and made of flint glass (dispersive power = 0.03) is kept in contact with a thin concave lens of focal length 20 cm and made of crown glass. Calculate the dispersive power of crown glass if the above said combination acts as an achromatic doublet. 
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45.

Electrons, initially at rest, are passed through a potential difference of 2 kV. Calculate their:  

(i) Final velocity and

(ii) de Broglie wavelength.

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