### Chapter 20 - Electromagnetism - 2 1. Transformer works on the principle of self induction a) True b) False 2. Transformer is used as an important part of most ofthe electronic devices. a) True b) False 3. There is only one coil in a transformer. a) True b) False 4. A bar magnet has north and south poles. a) True b) False 5. If we grasp the current carrying conductorin our right hand with the stretched thum, then tumb shows the direction of a) Magnetic field b) Electric field c) Electric current d) Magnetic flux 6. The shape of magnetic lines force in case of a straight current carrying conductor is a) Elliptical b) Triangular c) Rectangular d) Circular 7. When a straight current carrying conductor is placed in a magnetic field at right angles to it the direction of force acting upon it is a) Same as the direction of field b) Opposite to the direction of field c) Makes and angle of 45 degree with the current d) At right angles to both the field and the current 8. In an electric curcuit a switch key is used for a) Switch on flow of current b) Swith off to flow of current c) Both for on and off current d) None of the above 9. When a current carrying conductor is placed at an angle theta with a magnetic field then force is directly propotional to a) Cos theta b) Tan theta c) Sin theta d) All of the above 10. If the conductor is placed parallel to the field, force act upon the conductor is a) Maximum b) Minimum c) Zero d) Constant 11. In D.C. motor spindle of the coil is fixed with the ring made up of a) Iron b) Steel c) Silver d) Copper 12. In mutual induction current induced in one circuit is due to change of current in another in a) Another circuit b) Same circuit c) Both circuits d) None of the above 13. The coil in which the change in the current produces induced current in another coil known as a) First coil b) Primary coil c) Secondary coil d) Second coil 14. When current passes through a coil, it produces a magnetic field, which one of the following pass through turns of the coil a) High voltage b) Magnetic flux c) Lines of force d) Steady current 15. According to the right hand rule, if the current flows from bottom end to top then the direction of the lines of force are a) Clock wise b) Anti clockwise c) Both clock wise and anti clockwise d) None of the above 16. A closely wound cylindrical coil of insulated wire is called a) DC motor b) AC Generator c) Transformer d) Solenoid

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