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Q.
The dielectric strength of air is $2.0\times10^6 N/C$. The largest charge that a metallic sphere of $3 \,mm$ radius can hold is
Electrostatic Potential and Capacitance
Solution:
Dielectric strength is the maximum electric field that a pure material can withstand under ideal conditions without breaking down.
Here $E =\frac{ Q }{4 \pi \epsilon_{0} R ^{2}}$
$
\Rightarrow Q = E .4 \pi \epsilon_{0} R ^{2}=3 \times 10^{6} .\left(4 \pi \times 8.85 \times 10^{-12} \times 0.30^{2} \times 10^{-4}\right)=3 \times 10^{-9} C =3 nC
$