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A conducting sphere is enclosed by a hollow conducting shell. Initially the inner sphere has a charge Q. While the outer one is un charged. The potential difference between the two spherical surface is found to be V. Later on the outer shell is given a charge – 4Q. The new potential difference between the two surface.

a. 1V b. V c. – 2V d. 2V Answer: (b) \(\begin{array}{l}{{V}_{A}}=\frac{KQ}{a}+\frac{K(-Q+Q)}{b}\end{array} \) \(\begin{array}{l}{{V}_{B}}=\frac{KQ}{b}+\frac{K(-Q+Q)}{b}\end{array} \) \(\begin{array}{l}\Delta V=KQ\left( {}^{1}/{}_{a}-{}^{1}/{}_{b} \right)\end{array} \)... View Article

The density of a circular disc is given as σ = [latex]{{p}_{0}}X[/latex] where ‘X’ is the distance from the centre. Its moment of interia about an axis perpendicular to interia about an axis perpendicular to its plane and passing through its edge is:

a. \(\begin{array}{l}\frac{15}{16}{{P}_{0}}\pi {{R}^{5}}\end{array} \) b. \(\begin{array}{l}\frac{16}{15}{{P}_{0}}\pi {{R}^{5}}\end{array} \) c. \(\begin{array}{l}\frac{6}{5}{{P}_{0}}\pi {{R}^{5}}\end{array} \) d. \(\begin{array}{l}\frac{5}{6}{{P}_{0}}\pi {{R}^{5}}\end{array} \) Answer: (b) Using parallel... View Article

An elastic string of Length 42 cm and cross section area 10–4 m2 is attached between two pegs at distance 6mm as shown in the figure. A particle of mass m is kept at mid point of string stretched as shown in figure by 20 cm and released. As the string attains natural Length, the particle attains a speed of 20 m/s. Then young modulus Y of string is of order.

a. 108 b. 1012 c. 106 d. 104 Answer: (c) Elastic stream energy × volume = kinetic energy \(\begin{array}{l}Vol\times \frac{1}{2}stress\,\times... View Article

Dimension of [latex]sqrt{frac{{{varepsilon }_{0}}}{{{mu }_{0}}}}[/latex]are

a. \(\begin{array}{l}\left[ M{{L}^{2}}{{T}^{-3}}{{A}^{-2}} \right]\end{array} \) b. \(\begin{array}{l}\left[ {{M}^{-1}}{{L}^{-2}}{{T}^{3}}{{A}^{2}} \right]\end{array} \) c. \(\begin{array}{l}\left[ {{M}^{2}}{{L}^{2}}{{T}^{-3}}{{A}^{-2}} \right]\end{array} \) d. \(\begin{array}{l}\left[ {{M}^{-1}}{{L}^{2}}{{T}^{3}}{{A}^{2}} \right]\end{array} \)... View Article