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Question 84 of 122

Q.Van de Graaff generator consists of a hollow metal sphere of diameter 2 m. If the potential on the surface of the sphere is 6 million volt, the charge accumulated over the surface of the sphere is :

(a) 0.66 milli coulomb
(b) 1 coulomb
(c) 8.854 micro coulomb
(d) 0.33 micro coulomb
Puducherry TnboardTamil Nadu HSC (DGE) Board 2018MCQ· 1mImportance★★★★★
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The charge accumulated on the Van de Graaff sphere works out to about 0.66 millicoulomb.

A charged conducting sphere of radius RR carrying charge QQ has a surface potential V=14πε0QR=kQRV = \dfrac{1}{4\pi\varepsilon_0}\dfrac{Q}{R} = \dfrac{kQ}{R}, where k=9×109 N m2 C−2k = 9\times10^9\ N\,m^2\,C^{-2}.

Given: diameter =2 m⇒R=1 m=2\,m \Rightarrow R = 1\,m; V=6×106 VV = 6\times10^6\,V.

Q=VRk=(6×106)(1)9×109=6.67×10−4 C=0.667 milli coulomb≈0.66 milli coulombQ = \dfrac{VR}{k} = \dfrac{(6\times10^6)(1)}{9\times10^9} = 6.67\times10^{-4}\,C = 0.667\ \text{milli coulomb} \approx 0.66\ \text{milli coulomb}

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