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Question: Answered & Verified by Expert
An electric dipole consists of two opposite charges, each of magnitude $1.0 \mu \mathrm{C}$ separated by a distance of $2.0 \mathrm{~cm}$. The dipole is placed in an external field of $10^{5} \mathrm{NC}^{-1}$. The maximum torque on the dipole is
PhysicsElectrostaticsCOMEDKCOMEDK 2015
Options:
  • A $0.2 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
  • B $1 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
  • C $2 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
  • D $4 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
Solution:
1824 Upvotes Verified Answer
The correct answer is: $2 \times 10^{-3} \mathrm{~N}-\mathrm{m}$
$\begin{aligned}\left|q_{1}\right| &=\left|q_{2}\right|=1 \mu \mathrm{C}=10^{-6} \mathrm{C} \\ 2 l=2 \mathrm{~cm}=2 \times 10^{-2} \mathrm{~m} \\ E=10^{5} \mathrm{NC}^{-1} \\ \therefore \text { Maximum torque, } \tau_{\max } &=p E \sin 90^{\circ} \\ &=p E=q(2 \ddot{l}) E \\ &=10^{-6} \times 2 \times 10^{-2} \times 10^{5} \\ &=2 \times 10^{-3} \mathrm{~N}-\mathrm{m} \end{aligned}$

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