Unit-1.ELECTRO STATICS One mark questions Total number of one mark questions from this chapter – 4 Hint– Normally March question paper 2 questions chance from Textbook self evaluation. 1.Book Questions: (Refer Page No.40-42) 1. A glass rod rubbed with silk acquires a charge of +8 × 10-12 C. The number of electrons it has gained or lost 5 x 10 7 lost 2. The electro static force between two point charges kept at distance d apart, in a medium εr = 6, is 0.3 N. The force between them at the same separation in vacuum is 1.8 N 3. Electric field intensity is 400 Vm-1 at a distance of 2m from apoint charge. It will be 100 Vm- 1 at a distance 4 m (Mar 07) 4. Two point charges +4q and +q are placed 30cm apart. At whatpoint on the line joining them the electric field is zero? 20 cm from the charge 4q 5. A dipole is placed in a uniform electric field with its axis parallel to the field. It experiences neither a net force nor a torque (Mar 06, 07 , Oct 07) 6. A If a point lies at a distance x from the midpoint of the dipole, the electric potential at this point is proportional to (mar 11) 7. Four charges +q, +q, -q and –q respectively are placed at the corners A, B, C and D of a square of side a. the electric potential at the centre O of the square is zero (Oct 06) 8. Electric potential energy (U) of two point charges is (Mar 09, June 10 & 11) 9. The work done in moving 500μc charge between two points on equipotential surface is zero (June 07,10, Mar 08,10,oct 11) 10. Which of the following quantities is scalar? Electric potential (June 06 & 08, Mar 09, oct 10 & 11)) 11. The unit of permittivity is C2 N -1 m -2 (Oct 08, mar 08, june 11) 12. The number of electric lines of force originating from a charge of 1micro coulomb is 1.129 x 10 11 13. The electric field outside the plates of two oppositely charged plane sheets of charge density σ is zero (Mar 06 & 11, jun 11, Oct 09) 14. The capacitance of a parallel plate capacitor increase from 5μF to 60μF when a dielectric is filled between the plates. The dielectric constant of the dielectric is 12 (June 08, Oct 10) 15. A hollow metal ball carrying an electric charge produced no electric field at inside the sphere points. (June 06, Mar 10) 2. Additional Questions: Note: Prepare one marks from frictional electricity, coulomb’s law, electric field, electric lines of force, electric field intensity, dipole in uniform electric field, electric potential energy and equipotential surface, gauss law and its applications, dielectric and polarization effect, capacitor in series and parallel and Van De Graff generator and Prepare unit based questions for Electric field intensity, electric flux, permittivity, capacitance, electric dipole moment etc. 1. The unit of electric field intensity is NC-1 (or) VM-1 (Oct-06, June-08, Mar 09) 2. The unit of electric flux is Nm2 C-1 (Mar 06, June 09 Mar 11) 3. An electric dipole is kept in a non-uniform electric field it experiences a force and a torque (Mar 08,Oct 08) 4. The work done in moving 4μc charge from one point to another in an electric field is 0.012J. The potential difference between them is 3000 V (Mar 06) 5. Torque on a dipole in a uniform electric field is maximum when angle between P vector and E vector is 90° (June 06,Oct 09) 6. Potential energy of 2 equal negative point charges of magnitude 2μc placed 1 m apart in air is 0.036J (June 06) 7. The value of permittivity of free space is (Oct 06) 8. The principle used in lightning conductors is corona discharge (Oct 06) 9. Unit of electric dipole moment is Coulomb metre (cm) (Mar 07) 10. Which is not a dielectric Gold (June 07) 11. The electric potential energy of an electric dipole in an electric field is –PE cosθ. (Mar 07) 12. The direction of electric field at a point on the equatorial line due to an electric dipole is Parallel to the axis of the dipole and opposite to the direction of dipole moment (June 07) 13. When an electric dipole of dipole moment P is aligned parallel to the electric field E then the potential energy of the dipole is given as -PE (June 08) 14. A capacitor of capacitance 6μF is connected to a 100 V battery. The energy stored in the capacitor is 0.03J (Mar 08) 15. The equivalent capacitance of 2 capacitors in series is 1.5μƒ. The capacitance of one of them is 4μƒ. The value of capacitance of the other is 2.4 μƒ (Oct 07 & 09) 16. The law that governs the force between electric chargers is Coulomb’s law (Oct 07) 17. Quantization of electric charge is given by q = ne (Oct 08) 18. An example of conductor is human body (Oct 08) 19. The magnitude of the force acting on a charge of 2 x 10-10C placed in a uniform electric field of 10 Vm-1 is 2x10-9N (Mar 09) 20. The torque (τ) experienced by an electric dipole placed in a uniform electric field (E) at an angle (Ø) with the field is PE sin Ø (June 09) 21. The negative gradient of potential is electric field intensity (June 09) 22. When a point charge of 6μC is moved between 2 points in an electric field, the work done is 1.8 x 10-5J. the potential difference between the 2 points is 3V (Oct 09) 23. Van de Graff generator is used to accelerate both protons and deuterons. 24. The number of electric lines of force originating from a charge of 1mic25. The capacitance of a parallel plate capacitor increases from 5μF and 50μF, when the dielectric is filled between the plates, the dielectric constant of the dielectric is 10. (June 09) 26. 3 Capacitor of capacitance, 1μF, 2μf, 3μF, are connected in series. The effective capacitance of a capacitor is 6/11μF. (Mar 10) 27. An electric dipole of moment vector p is placed in a uniform electric field of intensity vector E at an angle θ with respect to the field. The direction of the torque is Perpendicular to the plane containing Vector p and E. (Mar 10) 28. Electric field intensity at a distance r due to a infinitely long straight charged wire is directly proportional to 1/r. (June 10) 29. The ratio of electric potential at point 10cm and 20cm from the centre of an electric dipole along its axial line is 4:1. (June 10) 30. The intensity of electric field at a point is equal to the force experienced by a charge q. (oct 10) 31. N capacitors each of capacitance C are connected in series. The effective capacitance is n c. (oct 11) 32. A non-polar dielectric is placed in an electric field (E). its induced dipole moment acts in the direction of E . (oct 11) 33. A dielectric medium is placed in an electric field. The field induced inside the medium acts opposite to electric field. (jun 11) 34. The intensity of the electric field that produces a force of 10-5N on a charge of 5micro coulomb is 2N C-1 (mar 11) 35. If the medium between the two charges is replaced by air, then the force between them increases. 36. The practical units of capacitance are μ F and pF. 37. Capacitance of a capacitor is independent of both the charge q and potential v. (oct 10) 38. Dielectric is also called as insulator 39. A device not working with the principle of electrostatic induction is microwave oven. 40. ‘Action of points’ is used in lightning conductor and vande graff generator. Unit -1. Electrostatics To Write 31 and 32 One question chance from the textbook self evaluation. Refer Page No. 42, 43. 1. Define electric potential at a point. (Mar 07 & June 09 ) Page No.12 2. What do you mean by “Additive nature of charge”? Give an example. Page No.3 (Oct 07) 3. What is a polar molecule? Give any two example? Page No.24 (Mar 07) 4. State Gauss’ Law in electrostatics Page No.17,18 (June & Oct 06,Mar,09,mar11) 5. What is meant by Dielectric Polarization? Page No.25(Oct 09,Oct 11) 6. Why it is safer to be inside a car than standing under a tree during lightning. Page No.21 (Mar 06,10,June 06 & 09) 7. Define ‘coulomb’ on the basis of coulomb’s law, explain it in vector form? Page No.3,4 (Mar 10, June 07,10,Oct 10,11) 8. Define relative permittivity and permittivity. How they are related. Page No.4 9. What is the unit of capacitances? Define it .What is capacitor? Page No.22 (Mar 09) 10. What are conductors and Insulators? Give example Page No.2 11. Give any three properties of electric line of force? (June 10) Page No.7 12. What is meant by electrostatic shielding? Where it is used. Page No.21 (Mar 08) 13. Define electric flux. Give its unit. Page No.17 (June 08) 14. Define Potential difference? Give its unit. Page No.12 15. Explain the working of microwave oven. Page No.12 (June 08) 16. What is meant by corona discharge (or) action of points? What are its advantages? Page No.30 (June 07, Oct 08) 17. Difference between polar and non-polar molecules. Page No.24 18. Write the application of capacitor. Page No.27 (Oct 07, Mar 11) 19. Distinguish between electric potential and potential difference. Page No.12 20. What is Gaussian surface and equipotential surface? Page No.16 21. What is an electric dipole? Define electric dipole moment. Page No.8 (Oct 09, June 11) 22. Define electric field intensity at a point in an electric field. What is its unit? Page No.6 23. Define coulomb. (Mar 06) Page No.4 24. What is a non-polar molecule? Give example (Oct 06, June 11,Oct 10 ) Page No.24 25. What is electric potential energy? Page No.11 26. What is meant by electric polarization? 27. Problems: from text book example, page no 35 to 39. 1.7, 1.8, 1.11, 1.12, 1.13, 1.14, 1.15 (model in Oct 08) 28. Problems: from book back, page no 43 to 45. 1.46, 1.47 1.50, 1.53 1.55, 1.58, 1.59 (Mar 08) Unit-1. ELECTROSTATICS To write 51 Total Questions: 15 Note: Normally problems more chance, from this chapter. (Text book examples or self evaluation). If problem is not given, chance from text book back Question. Compulsory problem is given in (June 07, June 11) (2 times) from this chapter. Refer Page No.42, 43 for book back questions. 1. Write the properties of electric lines of forces. Page No.7 (Mar 07 & 08, Oct -07,Mar 10,Oct 11, Mar 11) 2. Define electric potential at a point. Obtain an expression for electric potential due to a point charges. Page No.12,13 (Mar 09 ) 3. What is electrostatic potential energy of a system of two point charges? Deduce an expression for it. Page No.15,16 (Oct 09) 4. Prove that the energy stored in a parallel plate capacitors e is Page No.28 5. Explain working method of Van-de-Graaff generator. Page No.30,31 6. Deduce an expression for the capacitance of the parallel plate capacitor. Page No.26 (June 10) 7. Derive an expression for the torque acting on the electric dipole when placed in uniform electric field. (Oct 10) Page No.11 8. Explain the effect of introducing a dielectric slab between the plates of parallel plate capacitor. Page No.26 9. Deduce an expression for the capacitance of the parallel plate capacitor. Page No. 23 to 24 10. What is a capacitor? Explain the principle of a capacitor. Page No. 22 & 23 11. State Gauss law. Using this drive an expression for electric field due to two parallel charges sheets. Page No.19 & 20 12. State Coulomb’s law in electro statics and explain it in vector form. Page No. 3 13. State and explain the principle of super position in electro statics. Page No.5 14. Problem from text book examples (Vol.1) Page No.32 to 40 1.4, 1.5, 1.6, 1.7 (C.P.in June 07), 1.9 (Model paper), 1.10 15. Problems from book-back problems, Page No. 43-45 1.41, 1.42, 1.44, 1.45,1.46, 1.47, 1.49 (June 08), 1.53 (Oct 08), 1.54 (C.P. in June 07), 1.55, 1.56, 1.58, 1.59 (C.P.in June 11) (June 06, Oct 06) Book back problems 1.13(Mar 06), 1.16(June 09) 10 MARKS To write 63 NOTE: Chance from book question. Refer text book page no: 42, 43 (vol- 1) 1. What is an electric dipole? Derive an expression for the electric field due to an electric dipole at a point on its axial line. Page No. 8-9 (Mar 06 & 09, June 06, June 10, Oct 10) 2. Derive an expression for electric potential due at a point to an electric dipole discus the special cases. Page No.14-15 (Oct 06, Mar & June 08, Oct 11, Mar 10 ) 3. Deduce an expression for equivalent capacitance of capacitors connected Page No.27-28 (i) parallel (ii) series. (June 07, Oct 07) 4. Principle, construction and working of Van de Graaff generator. What is its use. Page No. 30- 31(Oct 08 & 09) 5. Derive an expression for electric field due to an electric dipole at a point along the equatorial line. Page No.9-10 (Mar 07, June 09) 6. Explain the principle of a capacitor. Deduce an expression for the capacitance of a parallel plate capacitor. What is capacitor? Page No.22-26 7. State Gauss’s law. Applying this calculate electric field due to (i) an infinitely long straight charged with uniform charge density (ii) an infinitely plane sheet of charge of q. Page No.17-19. (June 11) 8. What is dielectric? Explain the effect of introducing a dielectric slab between the plates of a parallel plate capacitor. Page No.24- 26 9. Define the electric potential at a point. Is it a scalar or vector quantity? Obtain an expression for electric potential due to a point charge. Page No.12-13 10. State Gauss law using this find an expression for electric field due to uniformly charged spherical shell at a point (i)outside the shell (ii) on the surface (iii)inside the shell.
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