2. Solved Papers
  3. VIT Engineering

VIT Engineering VIT Engineering Solved Paper-2010

  • question_answer
     An electric dipole consists of two opposite charges   of   magnitude   \[q=1\times {{10}^{-6}}C\] separated by 2.0 cm. The dipole is placed in an external field of\[1\times {{10}^{5}}N{{C}^{-1}}\]. What maximum torque does the field exert on the dipole? How much work must an external agent do to turn the dipole end to end, starring from position of alignment\[(9=0{}^\circ )\]?

    A)  \[4.4\times {{10}^{6}}N-m,\text{ }3.2\times {{10}^{-4}}J\]

    B)  \[-2\times {{10}^{-3}}N-m,\text{ }-4\times {{10}^{3}}J\]

    C)  \[4\times {{10}^{3}},\text{ }2\times {{10}^{-3}}J\]

    D)  \[2\times {{10}^{-3}}N-m,\text{ }4\times {{10}^{-3}}J\]

    Correct Answer: D

    Solution :

    \[q=\pm 1\times {{10}^{-6}}C\] \[2a=2.0cm=2.0\times {{10}^{-2}}m\] \[W=?,\,{{\theta }_{1}}={{0}^{o}},\,{{\theta }_{2}}={{180}^{o}}\] \[{{\tau }_{\max }}=pE=q(2a)E\] \[=1\times {{10}^{-6}}\times 2.0\times {{10}^{-2}}\times 1\times {{10}^{5}}\] \[=2\times {{10}^{-3}}Nm\] \[W=pE(\cos {{\theta }_{1}}-\cos {{\theta }_{2}})\] \[=({{10}^{-6}}\times 2\times {{10}^{-2}})({{10}^{5}})(\cos {{0}^{o}}-\cos {{180}^{o}})\] \[=4\times {{10}^{-3}}\,J\]  


You need to login to perform this action.
You will be redirected in 3 sec spinner