• # question_answer If the vertical components of earth's magnetic field be $6\times {{10}^{-5}}Wb/{{m}^{2}}$ then what will be the induced potential difference produced between the rails of metre gauge when a train is running on them with speed of$36\text{ }km/hr$? A)  $9\times {{10}^{4}}$volt        B)  $6\times {{10}^{-4}}$ voltC)  $3\times {{10}^{-4}}$ volt       D)  $2\times {{10}^{4}}$ volt

Vertical component of earth's magnetic field $B=6\times {{10}^{-5}}Wb/{{m}^{2}}$ distance between the meter gauge rail $l$                 =  1 metre speed of train $V=36\text{ }km/hr.$                 $=\frac{36\times 5}{18}=10\,m/s.$ The induced potential difference is given by             $\varepsilon =B\upsilon l=6\times {{10}^{-5}}\times 10\times 1$ $=6\times {{10}^{-4}}$ volt