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12 TH STANDARD PHYSICS EFFECTS OF ELECTRIC CURRENT Prepared by: R.RAJENDRAN, M.A., M.Sc., M.Ed., N. INGARAN, M.Sc., M.Phil.,M.Ed.,

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1. The electric iron works on the principle of ………… effect of current. a) thermo electric b) Joule’s heating c) Peltier d) magnetic CHOOSE THE CORRECT ANSWER

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2. The melting point of tungsten is ……………………… o C. a) 3000 b) 4000 c) 3380 d) 4380 CHOOSE THE CORRECT ANSWER

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3. Fuse wire has high resistance and ……………………… melting point. a) high b) low c) zero d) infinity CHOOSE THE CORRECT ANSWER

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4. The thermo emf is maximum at a temperature called …………temperature. a) neutral b) inversion c) critical d) Kelvin CHOOSE THE CORRECT ANSWER

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5. The unit of Peltier coefficient is ……………………… a) ampere b) ohm c) volt d) mho CHOOSE THE CORRECT ANSWER

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6. Thomson effect is zero for ……………………… a) copper c) iron c) mercury d) lead CHOOSE THE CORRECT ANSWER

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7. The unit of Thomson coefficient is ……………………… a) ampere b) volt / C c) volt d) ohm CHOOSE THE CORRECT ANSWER

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8. Thermopile is a device used to detect ………………………. a) light intensity b) sound intensity c) thermal radiations d) current CHOOSE THE CORRECT ANSWER

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9. The equation for the magnetic induction at the centre of the current carrying circular ring is B = ………… a) μ 0 nI / 2a b) 2a / μ 0 nI c) μ 0 nI / a d) 2μ 0 nI / a CHOOSE THE CORRECT ANSWER

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10. Tangent galvanometer works on the principle of ……………………… a) Ampere rule b) Maxwell’s right hand rule c) end rule d) tangent law CHOOSE THE CORRECT ANSWER

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11. The reduction factor of T.G. is given by the equation ……………………… a) μ 0 nI / 2a b) 2a / μ 0 nI c) 2aBh/ μ 0 n d) μ 0 n / 2aBh CHOOSE THE CORRECT ANSWER

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12. The magnitude of Lorentz force is F = ………………………. a) Bqv cosθ b) Bqv tanθ c) Bqv secθ d) Bqv sinθ CHOOSE THE CORRECT ANSWER

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13. The torque on a current carrying coil is maximum when the coil is ………………… to the magnetic field. a) parallel b) perpendicular c) inclined at an angle d) none of the above CHOOSE THE CORRECT ANSWER

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14. The deflection per unit voltage is called ……………sensitivity of a galvanometer. a) current b) voltage c) resistance d) conductance CHOOSE THE CORRECT ANSWER

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15. An ideal voltmeter is which has ……………………… resistance. a) zero b) infinite c) minimum d) maximum CHOOSE THE CORRECT ANSWER

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16. The product of the current and the loop area is called ………………………. a) dipole intensity b) magnetic dipole moment c) permeability d) permittivity CHOOSE THE CORRECT ANSWER

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17. The value of the gyromagnetic ratio is ……………………… C kg -1. a) 8.8 × 10 10 b) 9.27 × 10 -24 c) 4.8 × 10 10 d) 1.602 × 10 -19 CHOOSE THE CORRECT ANSWER

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18. The magnetic field in a moving coil galvanometer is the …… magnetic field. a) perpendicular b) radial c) crossed d) non-uniform CHOOSE THE CORRECT ANSWER

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19. The equation for force on a current carrying conductor in a magnetic field is F = ……… a) Bqv b) navd e c) Blv d) BIL CHOOSE THE CORRECT ANSWER

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20. Lawrence devised ……………………… a) cyclotron b) van de graff generator c) ac generator d) galvanometer CHOOSE THE CORRECT ANSWER

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21. For a given thermocouple, ……………… temperature is a constant. a) neutral b) inversion c) critical d) Kelvin CHOOSE THE CORRECT ANSWER

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22. Peltier effect is the converse of ……………………… effect. a) Thomson b) Ampere c) Seebeck d) Joule’s heating CHOOSE THE CORRECT ANSWER

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23. In transformers, dynamos ……………………… effect is undesirable. a) Thomson b) Ampere c) Seebeck d) Joule’s heating CHOOSE THE CORRECT ANSWER

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24. At the temperature of inversion, the thermo emf is ………………… a) minimum b) maximum c) zero d) infinity CHOOSE THE CORRECT ANSWER

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25. Thermal energy may be used to produce an emf. This is called …… effect. a) Joule’s law of heating b) photoelectric effect c) Peltier effect d) thermoelectric CHOOSE THE CORRECT ANSWER

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26. Joule’s law of heating is given by the equation H = ………………………. a) I 2 t b) V 2 Rt c) VIt d) IR 2 t CHOOSE THE CORRECT ANSWER

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27. The alloy of nickel and chromium is called ………………………. a) brass b) bronze c) silver d) nichrome CHOOSE THE CORRECT ANSWER

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28. The relation between the thermo emf and the temperature is V = ……………… a) αθ b) αθ + ½βθ 2 c) ½βθ 2 d) αθ + βθ 2 CHOOSE THE CORRECT ANSWER

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29. The amount of heat absorbed or evolved at one junction in Peltier effect is H = ……………………… a) I 2 t b) πIt c) VIt d) IR 2 t CHOOSE THE CORRECT ANSWER

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30. Sn, Au, Ag, Zn, Cd, Sb show ……………………… effect. a) Negative Thomson b) Positive Thomson c) Seebeck d) Joule’s heating CHOOSE THE CORRECT ANSWER

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31. Bi, Ni, Pt, Co, Fe, Hg show ……………………… effect. a) Negative Thomson b) Positive Thomson c) Seebeck d) Joule’s heating CHOOSE THE CORRECT ANSWER

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32. Seebeck effect is a ……………………… process. a) magnetic b) reversible c) irreversible d) electromagnetic CHOOSE THE CORRECT ANSWER

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33. The thermo emf produced in Bi- Ag thermo couple is …Bi-Sb thermo couple. a) larger than b) smaller than c) equal d) none of the above CHOOSE THE CORRECT ANSWER

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34. Peltier coefficient depends on pair of metals in contact and the………. of the junction. a) voltage b) resistance c) temperature d) none of the above CHOOSE THE CORRECT ANSWER

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35. The unit of the magnetic induction is ………………………. a) ampere b) ohm c) volt d) tesla CHOOSE THE CORRECT ANSWER

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36. The magnetic induction due to infinitely long straight conductor carrying current is B = ………………………. a) μ 0 I / 2a b) 2a / μ 0 nI c) 2aBh/ μ 0 n d) μ 0 I / 2πa CHOOSE THE CORRECT ANSWER

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37. Around a current carrying conductor magnetic field is associated. This was observed by ……………………… a) Ampere b) Oersted c) Ohm d) Faraday CHOOSE THE CORRECT ANSWER

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38. Tangent galvanometer is most sensitive for a deflection of ………………………. a) 30 degree b) 45 degree c) 60 degree d) 90 degree CHOOSE THE CORRECT ANSWER

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39. Tangent law is B = ……………………… a) BH Tan θ b) BH Sec θ c) BH Sin θ d) BH Cot θ CHOOSE THE CORRECT ANSWER

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40. ……………………… law can be written as ∫ B. dl = μ o I o. a) Maxwell’s right hand b) Ampere’ circuital c) Seebeck d) Joule’s heating CHOOSE THE CORRECT ANSWER

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41. When a charged particle moves in a circular path in a magnetic field, the time period is T = ………………………. a) Bq / 2m b) 2m / Bq c) 2πm / Bq d) Bq / 2πm CHOOSE THE CORRECT ANSWER

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42. The torque on a rectangular coil of wire in a magnetic field is …………………… a) nBIA tanθ b) nBIA cosθ c) nBIA sinθ d) nBIA secθ CHOOSE THE CORRECT ANSWER

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43. The deflection per unit current is called ……………………… sensitivity of a galvanometer. a) current b) voltage c) resistance d) conductance CHOOSE THE CORRECT ANSWER

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44. The current sensitivity is given by ( θ / I ) = ………………………. a) nCB / I b) nBAC c) BIl d) nBA / C CHOOSE THE CORRECT ANSWER

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45. To convert a galvanometer in to an ammeter, a …… resistance is connected in parallel with the galvanometer. a) low c) infinite c) high d) very high CHOOSE THE CORRECT ANSWER

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46. To convert a galvanometer in to a voltmeter, a ………… resistance is connected in series with the galvanometer. a) low b) very small c) high d) zero CHOOSE THE CORRECT ANSWER

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47. Bohr magneton value is ……………………… Am2. a) 8.8 X 10 10 b) 9.27 X 10 -24 c) 4.8 X 10 10 d) 1.602 X 10 -19 CHOOSE THE CORRECT ANSWER

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48. A current of 0.2 A flows through a circular loop of area 10 cm 2. The magnetic dipole moment is ………… Am 2 a) 9.27 X 10 -24 b) 8.8 X 10 10 c) 2 X 10 - 4 d) 2 CHOOSE THE CORRECT ANSWER

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49. In TG, a current of 1A produces a deflection of 30 . The current that produces a deflection of 60 is ……… A. a) 2 b) 3 c) 5 d) 1 CHOOSE THE CORRECT ANSWER

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50. The resistance of the tungsten wire of a 100W,220V bulb is ………………… ohm. a) 2.2 b) 220 c) 100 d) 484 CHOOSE THE CORRECT ANSWER

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51. Joule’s law of heating is (a) (b) H = V 2 Rt (c) H = VIt (d) H = IR 2 t CHOOSE THE CORRECT ANSWER

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52. Nichrome wire is used as the heating element because it has (a) low specific resistance (b) low melting point (c) high specific resistance (d) high conductivity CHOOSE THE CORRECT ANSWER

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53. Peltier coefficient at a junction of a thermocouple depends on (a) the current in the thermocouple (b) the time for which current flows (c ) the temperature of the junction (d) the charge that passes through the thermocouple CHOOSE THE CORRECT ANSWER

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54. In a thermocouple, the temperature of the cold junction is 20 C, the neutral temperature is 270 C. The temperature of inversion is (a) 520 C (b) 540 C (c) 500 C (d) 510 C CHOOSE THE CORRECT ANSWER

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55. Which of the following equations represents Biot-savart law? (a)(b) (c)(d) CHOOSE THE CORRECT ANSWER

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56. Magnetic induction due to an infinitely long straight conductor placed in a medium of permeability μ is (a) (b) (c) (d) CHOOSE THE CORRECT ANSWER

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57. In a tangent galvanometer, for a constant current, the deflection is 30 . The plane of the coil is rotated through 90 . Now, for the same current, the deflection will be (a) 30 (b) 60 (c) 90 (d) 0 CHOOSE THE CORRECT ANSWER

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58. The period of revolution of a charged particle inside a cyclotron does not depend on (a) the magnetic induction (b) the charge of the particle (c) the velocity of the particle (d) the mass of the particle CHOOSE THE CORRECT ANSWER

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59. The torque on a rectangular coil placed in a uniform magnetic field is large, when (a) the number of turns is large (b) the number of turns is less (c) the plane of the coil is perpendicular to the field (d) the area of the coil is small CHOOSE THE CORRECT ANSWER

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60. Phosphor – bronze wire is used for suspension in a moving coil galvanometer, because it has (a) high conductivity (b) high resistivity (c) large couple per unit twist (d) small couple per unit twist CHOOSE THE CORRECT ANSWER

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61. Of the following devices, which has small resistance? (a) moving coil galvanometer (b) ammeter of range 0 – 1A (c) ammeter of range 0–10 A (d) voltmeter CHOOSE THE CORRECT ANSWER

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62. A galvanometer of resistance G Ω is shunted with S Ω.The effective resistance of the combination is Ra. Then, which of the following statements is true? (a) G is less than S (b) S is less than Ra but greater than G. (c) Ra is less than both G and S (d) S is less than both G and Ra CHOOSE THE CORRECT ANSWER

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63. An ideal voltmeter has (a) zero resistance (b) finite resistance less than G but greater than Zero (c) resistance greater than G but less than infinity (d) infinite resistance CHOOSE THE CORRECT ANSWER

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Electrical Theory I - The Basics

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