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NEET 2021 · Electric Potential & Equipotentials

Electric Potential & Equipotentials question from NEET 2021

Q76NEET 2021Easy

Electric Potential & Equipotentials

Twenty seven drops of same size are charged at 220V each. They combine to form a bigger drop. Calculate the potential of the bigger drop.

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Answer: (a)

  1. Charge is conserved: Q=nqQ = nq; volume is conserved: 43πR3=n⋅43πr3⇒R=n1/3r\frac{4}{3}\pi R^3 = n\cdot\frac{4}{3}\pi r^3 \Rightarrow R = n^{1/3}r
  2. V′=kQR=knqn1/3r=n2/3VV' = \frac{kQ}{R} = \frac{knq}{n^{1/3}r} = n^{2/3}V
  3. V′=272/3×220=9×220=1980 VV' = 27^{2/3}\times 220 = 9 \times 220 = 1980\text{ V}
  4. So the answer is (a) 1980 V.
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