28/03/2020 Electromagnetic Induction(Senior Class Physics Study by Topics) 0Comments by Gate Academy Welcome to your Electromagnetic Induction(Senior Class Physics Study by Topics) NAME EMAIL PHONE NUMBER 1. Which of the following statements about magnetic field lines is not true? Magnetic field lines form open or closed loops.Magnetic field lines appear to begin at the north pole of a magnet.Magnetic field lines have no beginning or end.Magnetic field lines appear to end at the south pole of a magnet.2. A transformer with 5000 turns primary coil is designed to work from a 250V ac mains to give a supply of 10 V to ring an electric bell.The number of turns in the secondary coil of the transformer is1501002002503. A coil of area of cross section with 10 turns is in a plane which is perpendicular to an uniform magnetic field of The flux though the coil isZero10 Wb1 Wb100 Wb4. If a current carrying coil is mounted on a metal frame, the back emf induced in the coil causesdipole momentinductanceeddy currentselctromagnetism5. An emf of 12 V is induced when the current in the coil changes at the rate of. The coefficient of self induction of the coil is0.3 H0.003 H4.8 H30 H6. A wire moving at right angles to a magnetic field has NO induced voltageIf it is moving very fast.If the wire is covered with insulation.If it is made of copper.None of the above choices are correct.7. Alternating current can induce voltage because it hasvarying magnetic fieldhigh peak valueripple valuestronger magnetic field than direct current8. To convert alternating current dynamo into a direct current dynamo, theslip rings are replaced with a split ring commutatorstrength of the field magnet is increasednumber of the turns in the coil is increased9. On an ac generator which of the following does not apply ?commutatorslip ringsarmaturefield magnet10. The best material for the core of the primary and secondary coils of an induction coil issoft ironrubbercopper,steel11. A band of 500 rectangular loops of wire of area 20 cm by 20 cm, encloses a region of magnetic field which changes from 1.0T o 0.4T within 5 seconds, calculate the induced emf2.40 V5.60 V0.24 V24.0 V12. What is the magnetic flux linked by a coil when the normal to the coil and the direction of the magnetic field lines are parallel? Magnetic flux x area (and measured in Webers)Magnetic flux density x area (and measured in Webers)Magnetic flux x area (and measured in Teslas)Magnetic flux density x area (and measured in Teslas)13. A conductor of length 1 m moves with a velocity of 50 m/s at an angle of 30° to the direction of a uniform magnetic field of flux density 1.5 Wb/m. What is the emf induced in the conductor?50.5 V75.0 V37.5 V80.5 V14. A transformer steps down from 240 V to 12.0 V and supples a 12.0 V 24.0 W lamp. What is the efficiency of the transformer if the current drawn from the 240V supply is 0.120 A?57.2%83.3%100%66.6%15. A transformer with 5000 turns primary coil is designed to work from a 250V ac mains to give a supply of 10 V to ring an electric bell.Which of the following statement is correct?No energy is lost in the transformerIt is a step up transformerIt is a step down transformerIt will work if connected to 250 V dc mains16. Lenz's law is a law of the conservation ofElectric chargeEnergyMomentumElectric current17. A DC of 5A produces the same heating effect as an AC ofNone of these5 A rms current50 A rms current5 A peak current18. The ratio of primary and secondary turns in a transformer is 1: 200. If 220-volt a.c. is fed to primary, the voltage across secondary will be 220 V40 k V44 V220/200 V19. A circuit has an area of 0.4 m² and consists of 50 loops of wire. If the loops are twisted and allowed to rotate at a constant angular velocity of 10 rad/s in a uniform magnetic field of 0.4 T, the amplitude of the induced voltage is20 V16 V8 V80 V20. Carbon particles are used in carbon microphones becausethey are good conductorsthey amplify the soundtheir resistance changes with pressuretheir resistance changes with temperature21. A primary winding of a transformer has 400 turns and its secondary has 100 turns. If a source of emf for 12 V is applied to the primary, the secondary emf will be3 V6 V48 V24 V22. The induction coil works on the same principle asa dc generatora capacitoran ac generatora transformer23. The current in the primary coil of a transformer is 2.5A. If the coil has 50 turns and secondary 250 turns, calculate the current in the secondary coil. (Neglect energy loss in the transformer)0.2A5.0 A0.5 A2.5 A24. A magnet is moved through a coil of wire. The emf produced in the wire depends onthe strength of the magnetall of the abovethe speed at which the magnet is movedthe number of turns in the coil25. Transformers use ac so there will be the required Change in magnetic field for operation.Voltage for transformation.Transfer of energy from coil to coil.Change in input current.26 out of 25Time is Up!