Title 06. ELECTROMAGNETIC INDUCTION.pdf ✅

(3) induced electric current is clockwise (4) ring will come to rest 8. An of is induced in a metal rod of length held normal to a uniform magnetic field of , when moves with a velocity of (1) (2) (3) (4) 9. When a sheet of metal is placed in a magnetic field, which changes from zero to a maximum value, the induced currents are set up in the di‐ rection shown in figure. What is the direction of magnetic field? (1) West to East (2) Out of the plane of the paper (3) South to North (4) Into the plane of the paper 10. The back e.m.f. induced in a coil, when current changes from 1 ampere to zero in one millisec‐ ond, is 4 volts, the self-inductance of the coil is (1) (2) (3) (4) 11. Two coils have mutual inductance . The current changes in the first coil according to equation , where and . The maximum value of emf in volt in the second coil is: (1) (2) (3) (4) 12. Assertion : The possibility of an electric bulb fusing is higher at the time switching ON and OFF. Reason : Inductive effects produces a surge at the time of switch OFF and switch ON (1) Both Assertion and Reason are cor- rect and Reason is the correct explana- tion of the Assertion. (2) Both Assertion and Reason are cor- rect but Reason is not the correct explana- tion of the Assertion. (3) Assertion is cor- rect but Reason is incorrect. (4) Assertion is incor- rect but reason is correct. 13. An average induced e.m.f. of appears in a coil when the current in it is changed from in one direction to in opposite direction in . Self-inductance of the coil is (1) (2) (3) (4) 14. A metal conductor of length rotates verti‐ cally about one of its ends at an angular velocity of . If the horizontal component of earth's magnetic field is , then the developed between the two ends of conductor. (1) (2) (3) (4) 15. A generator has an of and in‐ ternal resistance of . Its terminals are connected to a load of . The voltage across the load is (1) (2) (3) (4) 16. A coil is placed in magnetic field such that plane of coil is perpendicular to the direction of magnetic field. The magnetic flux through a coil can be changed (A) By changing the magnitude of the magnetic field within the coil. (B) By changing the area of coil within the mag‐ netic field. (C) By changing the angle between the direction of magnetic field and the plane of the coil. (D) By reversing the magnetic field direction abruptly without changing its magnitude. (1) and only (2) and only (3) and only (4) and only 17. An average induced e.m.f of appears in a coil when the current in it is changed from in one direction to in opposite direction in . Self- inductance of the coil is: (1) (2) (3) (4) 18. Statement A : The back emf in a dc motor is maximum when the motor has just been switched on. Statement B : When motor is switched on, it has maximum speed. (1) Statement A is correct but Statement B is incorrect. (2) Statement A is in- correct but Statement B is correct. (3) Both statements are correct. (4) Both Statements are incorrect. emf 0.08 V 10 cm 0.4T 3.2 ms −1 2 ms −1 0.5 ms −1 20 ms −1 4 × 10 −3H 10 −3H 4H 1H 0.001H I = I0 cos ωt I0 = 20 A ω = 100π rad s −1 12π 8π 2π 6π 1 V 10 A 10A 0.5 sec 25 mH 75 mH 100 mH 50 mH 2 m 50 rad/ sec 0.5 T EMF 5 V 50 V 15 V Zero e. m. f. 440 volt 4000 hm 4000 ohm 220 volt 440 volt 200 volt 400 volt A C A, B C A, B D A B 1 V 10 A 10 A 0.5 sec 25 mH 50 mH 75 mH 100 mH