The radius of a conducting spherical shell is 10 mm and a 100 μC charge is spread on it. The force acting on a 10 μC charge placed at its centre is ...... (k=9×10⁹ N m² C⁻²)

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(3) zero. Given: shell of radius R=10 mm carrying Q=100 μC; a test charge q=10 μC at the centre. Idea: the charge on a conducting shell sits on its surface, and inside a charged shell the field is zero. Gauss's law: a sphere of radius r<R drawn inside the shell encloses no charge, so E (4π r²)=0⇒ E=0 everywhere inside. Force on the charge at the centre: F=qE=q×0=0 Physically, each bit of charge on the shell is matched by an equal bit diametrically opposite, and their pulls on the centre cancel. So the force is zero; the values of R, Q and k are not needed.

The radius of a conducting spherical shell is 10 mm and a 100 μC charge is spread on it. The force acting on a 10 μC charge placed at its centre is ...... (k=9×10⁹ N m² C⁻²)

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