**ElectroStatics**

(At present all the questions are posted together; soon we will be categorizing according to marks)

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- What is Frictional electricity? (1)
- When can we say that a body is charged?(1)
- What is electric charge? Is it a scalar or a vector quantity? (1)
- What is electrostatics? (1)
- Describe an experiment to show that there are two kinds of charges. (2)
- Describe an experiment to show that like charges repel and unlike charges attract. (2)
- Describe the electronic theory of frictional electricity. (2)
- Write the differences between conductors and insulators. (2)
- What is meant by electrostatic induction?
- Distinguish charging by induction and charging by conduction. (2)
- How can you charge a piece of metal positively without touching it? (2)
- Explain the additive nature of electric charge. (2)
- What do you mean by quantization of electric charge? (1)
- Calculate the number of electrons missing in a body with 1 coulomb positive charge. (1)
- If a body loses 10
^{9}electrons every secon, calculate the time required by it to acquire 1 C positive charge. - Estimate the charge constituted by the total number of electrons present in a cup of water.
- Determine the total charge of 1 kg of electrons.
- State the law of conservation of charge. (1)
- Write the difference between mass and charge. (2)
- State Coulomb’s law in electrostatics. (1)
- Define one coulomb. (1)
- Express Coulomb’s law in vector form. (1)
- Express coulomb’s law in terms of position vectors.
- State the principle of superposition of electrostatic forces.
- Show that coulomb’s force obeys Newton’s III law.
- Define permitivity of a medium.
- Define relative permitivity of a medium
- Define relative permitivity of a medium on the basis of Coulomb’s law.
- The electrostatic force of repulsion between two positively charged bodies is 3.7 x 10
^{-9}N, when they are separated by a distance of 5 A^{o }How many electrons are missing in each?

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### LONG ANSWER QUESTIONS

- Obtain an expression for the electric field intensity due to a uniformly charged ring of radius r at a point on the axis of the ring.
- Express Coulomb’s law in vector for.
- Derive an expression for the electric field due to an electric dipole at a point on (a) the axial line (b) the equatorial line.
- Derive an expression for the torque acting on an electric dipole placed in a uniform electric field.
- Show that the work done in rotating an electric dipole of dipole moment p in a uniform electric field E by an angle Î¸ from the equilibrium postition W = PE(1-cos Î¸)
- Derive Coulomb’s law from Gauss’ law.
- Use Gauss theorem to derive an expression for the electric field at a point due to an infinite plane sheet of charge of uniform charge density Ïƒ
- Use Gauss theorem to derive an expression for the electric field at a point due to a thin infinitely long straight lineÂ of charge of uniform charge density Î»
- Derive an expression for the electric field at a point due to uniformly charged spherical shell using Gauss’ law.
- Derive an expression for the capacitance of a parallel plate capacitor.
- Find the equivalent capacitance of three capacitors of capacitances C1, C2 and C3 connected in (1) series (2) parallel
- Derive an expression for the electric potential due to a point charge q at a distance r from it.
- Giving a labeled diagram explain the principle and working of a Van de Graaff generator.
- A dielectric slab of thickness t introduced between the plates of a parallel plate capacitor separated by a distance d. (t < d). DEerive an expression for the capacitance of the capacitor.

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