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# Question 31: NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance

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Question 31: NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance

1. Two large conducting spheres carrying charges Q1 and Q2 are brought close to each other, is the magnitude of electrostatic force between them exactly given by  r is the distance between their centres?
2. If coulomb’s law involved 1 /r3 dependence (instead of 1/r2), would Gauss’s law be still true?
3. A small test charge is released at rest at a point in an electrostatic field configuration. Will it travel along the field line passing through that point?
4. What is the work done by the field of a nucleus in a complete circular orbit of the electron? What if the orbit is elliptical?
5. We know that electric field is discontinuous across the surface of a charged conductor. Is electric potential also discontinuous there?
6. What meaning would you give to the capacitance of a single conductor?
7. Guess a possible reason why water has a much greater dielectric constant {- 80) then say, mica (= 6).
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1. Solution:

1. No, because coulomb’s law holds good only for point charges. ‘
2. No, because in that case electric flux linked with the closed surface will also become dependent on V other than charge enclosed by it.
3. No, it will travel along the field line only if it is a straight line.
4. Zero, whatever may be the shape of orbit may be. It is because work done in moving a charge in closed path in electric field is zero, as electric field is a conservative field.
5. No, electric potential is continuous
there. As E = 0, so  = 0 or V = constant.
6. It means that a single conductor is a capacitor whose other plate can be considered to be at infinity.
7. A water molecule is a polar molecule with non-zero electric dipole moment, however mica does not have polar molecules. So, dielectric constant of water is high.

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NCERT Solutions for 12th Class Physics: Chapter 2-Electrostatic Potential and Capacitance

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