Electrostatics Question 711
Question: A liquid drop having 6 excess electrons is kept stationary under a uniform electric field of$ 25.5KV{{m}^{-1}} $ . The radius of the drop is (neglect buotany)
Options:
A) $ 4.3\times {{10}^{-7}}m $
B) $ 7.3\times {{10}^{-7}}m $
C) $ 0.078\times {{10}^{-7}}m $
D) $ 3.4\times {{10}^{-7}}m $
Show Answer
Answer:
Correct Answer: B
Solution:
[b] $ F=qE=mg(q=6e=6\times 1.6\times {{10}^{-19}}) $
Density [d] $ \frac{\text{mass}}{\text{volume}}=\frac{m}{\frac{4}{3}\pi r^{3}}\text{ or }r^{3}=\frac{m}{\frac{4}{3}\pi d} $
Putting the value of v and m (= 2E/g) and solving we get $ r=7.8\times {{10}^{-7}}m $
