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1. Electric Charges and Fields
hard
Two small spherical balls each carrying a charge $Q = 10\,\mu C$ ($10$ micro-coulomb) are suspended by two insulating threads of equal lengths $1\,m$ each, from a point fixed in the ceiling. It is found that in equilibrium threads are separated by an angle ${60^o}$ between them, as shown in the figure. What is the tension in the threads......$N$ (Given: $\frac{1}{{(4\pi {\varepsilon _0})}} = 9 \times {10^9}\,Nm/{C^2}$)
A
$18$
B
$1.8$
C
$0.18$
D
None of the above
Solution
(b) In the following figure, in equilibrium $F_e = T \,sin \,30^o, r = 1\,m$
$==>$ $9 \times {10^9}.\frac{{{Q^2}}}{{{r^2}}}$ $=$ $T \times \frac{1}{2}$
$==>$ $9 \times {10^9}.\frac{{{{(10 \times {{10}^{ – 6}})}^2}}}{{{1^2}}} = T \times \frac{1}{2}$ $ \Rightarrow $$T$ $= 1.8 \,N$
Standard 12
Physics
