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Question

The transformed equation of $\frac{\partial^{2} u}{\partial x^{2}} + \frac{\partial^{2} u}{\partial y^{2}} = 0$ into polar coordinates is :

The correct answer is
$\frac{\partial^{2} u}{\partial r^{2}} + \frac{1}{r} \frac{\partial u}{\partial r} + \frac{1}{r^{2}} \frac{\partial^{2} u}{\partial \theta^{2}} = 0$

Laplace Equation in Polar Coordinates

The given equation is Laplace's equation in Cartesian coordinates:

$ \frac{\partial^{2} u}{\partial x^{2}} + \frac{\partial^{2} u}{\partial y^{2}} = 0 $

We need to transform this equation into polar coordinates ($r, \theta$), where $x = r \cos \theta$ and $y = r \sin \theta$.

Coordinate Transformation Formula

The Laplacian operator ($\nabla^2$) in polar coordinates is given by the formula:

$ \nabla^2 u = \frac{\partial^{2} u}{\partial r^{2}} + \frac{1}{r} \frac{\partial u}{\partial r} + \frac{1}{r^{2}} \frac{\partial^{2} u}{\partial \theta^{2}} $

Transformed Equation

Setting the Laplacian in polar coordinates equal to zero gives the transformed Laplace equation:

$ \frac{\partial^{2} u}{\partial r^{2}} + \frac{1}{r} \frac{\partial u}{\partial r} + \frac{1}{r^{2}} \frac{\partial^{2} u}{\partial \theta^{2}} = 0 $

This matches Option A.

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Important Questions from Miscellaneous

  1. Which of the following relationships is/are not true?
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    (B). PV = $\frac{3}{2}kT$
    (C). Compressibility factor Z = $\frac{pV}{nRT}$
    (D). Average kinetic energy of gas = $\frac{1}{2}kT$
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  2. Match List-I with List-II
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    (A). ns$^2$(I). 2100
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    (C). ns$^2$np$^3$(III). 800
    (D). ns$^2$np$^6$(IV). 900

    Choose the correct answer from the options given below:
  3. The shielding constant of a 2p electron (calculated using Slater's rules) is
  4. Match List-I with List-II
    List-IList-II
    SpectroscopyProperty
    (A). Raman(I). Polarizability
    (B). FTIR(II). Dipole Moment
    (C). UV-Visible(III). Absorbance
    (D). NMR(IV). Spin

    Choose the correct answer from the options given below:
  5. The structure of protein comprises of:
    (A). Primary structure of protein is associated with amino acids
    (B). Secondary structure of protein is associated to peptides
    (C). Tertiary structure of protein is associated with polypeptide chains
    (D). Quaternary structure of protein is associated with polypeptide chains
    Choose the correct answer from the options given below:
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