NATIONAL INSTITUTE OF OPEN SCHOOLING

Section A - Multiple Choice Questions

1. Which of the following statement is correct for two charged bodies?

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   • A. Like charges attract each other
   • B. Unlike charges repel each other
   • C. Like charges repel each other
   • D. Neutral bodies always repel charged bodies
2. If Q is the charge on a body and e is the electronic charge, quantisation of charge is expressed as:

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   • A. Q = e / N
   • B. Q = Ne
   • C. Q = N + e
   • D. Q = N / e
3. According to Coulomb's law, electrostatic force between two point charges varies as:

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   • A. r
   • B. 1 / r
   • C. 1 / r²
   • D. r²
4. The SI unit of electric field is:

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   • A. J C^-1
   • B. N C^-1
   • C. C N^-1
   • D. V m
5. The direction of electric dipole moment is from:

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   • A. negative charge to positive charge
   • B. positive charge to negative charge
   • C. centre to infinity
   • D. along the electric field always
6. The electric potential due to a dipole at every point on its equatorial line is:

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   • A. maximum
   • B. minimum
   • C. zero
   • D. infinite
7. Gauss's law relates electric flux through a closed surface to:

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   • A. electric potential on the surface
   • B. total charge enclosed by the surface
   • C. area of the surface only
   • D. charge outside the surface only
8. The electric field due to an infinitely long straight charged wire varies as:

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   • A. 1 / r
   • B. 1 / r²
   • C. r
   • D. independent of r
9. The electric field due to a uniformly charged infinite plane sheet is:

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   • A. proportional to r
   • B. inversely proportional to r
   • C. inversely proportional to r²
   • D. independent of distance from the sheet
10. Electric potential is a:

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    • A. vector quantity
    • B. scalar quantity
    • C. tensor quantity
    • D. dimensionless quantity
11. One volt is equal to:

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    • A. 1 coulomb per joule
    • B. 1 joule per coulomb
    • C. 1 newton per coulomb
    • D. 1 joule per newton
12. Capacitance of a capacitor is defined by:

    [1]
    • A. C = V / Q
    • B. C = QV
    • C. C = Q / V
    • D. C = Q² / V
13. For a parallel plate capacitor, capacitance is directly proportional to:

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    • A. distance between the plates
    • B. plate area
    • C. square of distance between plates
    • D. reciprocal of permittivity
14. The equivalent capacitance in series combination is:

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    • A. greater than every individual capacitance
    • B. equal to the sum of capacitances
    • C. less than the smallest capacitance
    • D. always equal to zero
15. The energy stored in a capacitor is given by:

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    • A. U = CV
    • B. U = 1/2 CV²
    • C. U = Q / V
    • D. U = V / 2C
16. On introducing a dielectric between the plates of a capacitor, its capacitance:

    [1]
    • A. decreases
    • B. becomes zero
    • C. remains unchanged
    • D. increases

Section B - Short Answer Questions

17. State any two basic properties of electric charge.

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18. What is meant by conservation of charge? Illustrate it using a glass rod rubbed with silk.

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19. Define quantisation of charge. Why can a body not possess 2.5e charge?

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20. Write Coulomb's law in scalar form and name the factors on which electrostatic force depends.

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21. Define electric field intensity at a point. Write its expression for a point charge q at distance r.

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    E = (1 / 4πε₀) (q / r²)
22. What is an electric dipole? Write the expression for its dipole moment.

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    p = q(2l)
23. Give any two properties of electric field lines.

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24. State Gauss's law for electrostatics.

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    Φ_E = q_enclosed / ε₀
25. Define electric potential at a point. Why is it a scalar quantity?

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26. Write the relation between potential difference and work done in moving a test charge q₀ from A to B.

    [2]
    V_B - V_A = W_AB / q₀
27. Define capacitance and state its SI unit.

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28. What is dielectric constant or relative permittivity? Write one relation involving K.

    [2]
    K = C / C₀ = ε / ε₀

Section C - Very Short Answer Questions

29. A body has charge 4.8 × 10^-19 C. How many electronic charges does it possess?

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30. Two equal point charges of 2 × 10^-6 C each are 3 m apart in vacuum. Calculate the force between them.

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31. Find the electric field due to a point charge 5 × 10^-9 C at a distance of 0.10 m in air.

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32. An electric dipole has charges ±4 × 10^-6 C separated by 5 × 10^-3 m. Calculate its dipole moment.

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33. What is the electric field inside a uniformly charged spherical shell?

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34. Calculate the potential at a point 0.20 m from a charge of 8 × 10^-9 C.

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35. A capacitor stores 6 × 10^-4 C charge at a potential difference of 200 V. Find its capacitance.

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36. Three capacitors of 2 μF, 3 μF and 5 μF are connected in parallel. Find the equivalent capacitance.

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37. A 4 μF capacitor is connected to a 12 V battery. Calculate the energy stored in it.

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Section D - 3 Mark Questions

38. Derive the expression for electric field intensity at a point on the axial line of a short electric dipole.

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39. Using Gauss's law, obtain the expression for electric field due to a long straight uniformly charged wire.

    [3]
40. Define electric potential due to a point charge and derive the expression:

    [3]
    V = (1 / 4πε₀) (q / r)
41. Derive the equivalent capacitance of two capacitors connected in series. What is the nature of charge and potential difference in series grouping?

    [3]

Section E - 5 Mark Questions

42. State Gauss's law and use it to derive the expression for electric field due to a uniformly charged spherical shell at:

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    (a) an external point
    (b) a point on the surface
    (c) an internal point
43. Explain the construction and principle of a parallel plate capacitor. Derive the expression for its capacitance in air and state the effect of inserting a dielectric slab between the plates.

    [5]