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Two opposite and equal charges 4 \times 10^{-8} coloumb when placed 2\times 10^{-2} coloumb

 away, form a dipole. If this dipole is placed in an external electric field

4\times 10^{8} newton/coloumb , the value of maximum torque and the work done in rotating

it through 180 \degree  will be

  • Option 1)

    64\times 10^{-4} Nm..and .. 64\times 10^{-4}J

  • Option 2)

    32\times 10^{-4} Nm..and .. 32\times 10^{-4}J

  • Option 3)

    64\times 10^{-4} Nm..and .. 32\times 10^{-4}J

  • Option 4)

    32\times 10^{-4} Nm..and .. 64\times 10^{-4}J

 

Answers (1)

best_answer

As we have learned

Work done in rotation -

W=PE\left ( \cos \Theta _{1} -\cos \Theta _{2}\right )

- wherein

 

 

Dipole moment p = 4 ´ 10–8´ 2 ´ 10–4 = 8 ´ 10–12m

Maximum torque = pE = 8 ´ 10–12´ 4 ´ 108

= 32 ´ 10–4Nm

Work done in rotating through 180o = 2pE

= 2 ´ 32 ´ 10–4 = 64 ´ 10–4J

 


Option 1)

64\times 10^{-4} Nm..and .. 64\times 10^{-4}J

Option 2)

32\times 10^{-4} Nm..and .. 32\times 10^{-4}J

Option 3)

64\times 10^{-4} Nm..and .. 32\times 10^{-4}J

Option 4)

32\times 10^{-4} Nm..and .. 64\times 10^{-4}J

Posted by

prateek

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