Conducting spheres and are touching and are initially neutral

PHYSICS · Single correct · A Level · Physics · Fields and their consequences · Fields and their consequences

Problem

Conducting spheres

A

and

B

are touching and are initially neutral. Sphere

A

has radius

4.0\,\text{cm}

, and sphere

B

has radius

6.0\,\text{cm}

. A negatively charged rod is brought close to sphere

A

without touching. While the rod is held in place, sphere

B

is momentarily connected to ground and then the grounding connection is removed. The rod is withdrawn, and the spheres are separated so that their centers are

0.20\,\text{m}

apart. The charge on sphere

B

is measured to be

+8.0\,\text{nC}

. Which of the following is closest to the magnitude of the electric force that sphere

B

exerts on sphere

A

after separation? (a)

1.9\,\mu\text{N}

(b)

9.6\,\mu\text{N}

(c)

38\,\mu\text{N}

(d)

96\,\mu\text{N}

Related theory

Conservation of Charge
Electric Charge
Coulomb's Law
Electric Force
Coulomb's law and superposition of forces
Electric Charges and Fields

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