InterviewSolution
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InterviewSolution
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Let B be the midpoint of AC. Two point charges Q are placed at A and C. What should be the value of charge placed at B so that the system remains at equilibrium?(a) –Q/2(b) –Q/4(c) +Q/2(d) +Q/4I have been asked this question in my homework.My question comes from Coulomb’s Law in section Charges and Fields of Physics – Class 12 |
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Answer» RIGHT option is (b) –Q/4 For EXPLANATION I would say: Whatever the value of q be, it will undergo equal force on both sides, hence q will be steady. Now, for stability of Q, NET force on Q must be ZERO. \(\FRAC {1}{4\pi\epsilon_o} \, \frac {Q^2}{d^2} + \frac {1}{4\pi\epsilon_o} \, \frac {Q.q}{(\frac {d}{2})^2}\) = 0 ⇒ \(\frac {Q^2}{d^2} = \frac {-Q q}{\frac {d^2}{4}}\) ⇒ Q = -49 ⇒ q = –\(\frac {Q}{4}\) |
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