Electrostatics 1 Question 20
21. Two small balls having equal positive charges $Q$ (coulomb) on each are suspended by two insulating strings of equal length $L$ (metre) from a hook fixed to a stand. The whole setup is taken in a satellite into space where there is no gravity (state of weightlessness). The angle between the strings is …… and the tension in each string is ………. newton.
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Answer:
Correct Answer: 21. $180\degree , \frac{Q^{2}}{16 \pi \varepsilon_{0} L^{2}}$
Solution:
- Due to electrostatic repulsion the charges will move as farthest as possible and the angle between the two strings will be $180^{\circ}$ as shown in figure. Tension in each string will be equal to the electrostatic repulsion between the two charges. Thus,
$$ T=F_{e}=\frac{1}{4 \pi \varepsilon_{0}} \frac{Q \times Q}{(2 L)^{2}}=\frac{Q^{2}}{16 \pi \varepsilon_{0} L^{2}} $$
