28/03/2020 Electromagnetic Induction(Senior Class Physics Study by Topics) 28/03/2020 0Comments by Gate Academy Welcome to your Electromagnetic Induction(Senior Class Physics Study by Topics) NAME EMAIL PHONE NUMBER 1. In an AC circuit the applied emf e = Eo sin (ωt + π/2) leads the current I = Io sin (ωt – π/2) by π/4 π π/2 0 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.Which of the following statement is correct? It is a step down transformer No energy is lost in the transformer It is a step up transformer It will work if connected to 250 V dc mains 3. Lenz's law is in accordance with the law of Conservation of charges Conservation of flux Conservation of energy Conservation of momentum 4. Two separate inductors of 50 and 150 mH respectively are mounted so that the mutual inductance inductance between them is 40 mH.What will be the resulting inductance if they are connected in series opposing 178 mH 73 mH 24 mH 120 mH 5. The induction coil works on the same principle as an inductor a dc generator a transformer an ac generator 6. 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 emf 24.0 V 2.40 V 0.24 V 5.60 V 7. A closed coil of wire is placed near a magnet. The magnet lies along the axis of the coil. Under which of the following conditions would there be no current in the coil? when the coil is moved away from the stationary magnet when both the coil and the magnet are held stationary when the coil is moved towards the stationary magnet 8. Since more magnetic field lines cross the area that is near the pole of a magnet, what does this indicate about the magnetic field strength in that location? It is stronger. It is leaving the magnet It is entering the magnet. It is weaker. 9. When there is an EMF, the direction of the current will always be such that (the magnetic field caused by it) will try to oppose the change producing it. Whose law is this? Boltzmann's Law Maxwell's Law Faraday's Law Lenz's Law 10. On an ac generator which of the following does not apply ? armature field magnet commutator slip rings 11. A transformer which can produce 8 V from a 240 V ac supply, as an efficiency of 80%. If the current in the secondary coil is 15 A, calculate the current in the primary coil 6.250 A 2.500 A 1.600 A 0.625 A 12. A DC of 5A produces the same heating effect as an AC of 5 A peak current None of these 5 A rms current 50 A rms current 13. The energy stored in an inductor of inductance 5mH when a current of 6A flows through it is 1¯−¹−² 1.4 x 10-² J 9.0 x 10-² J 1.8 x 10-² J 14. The number of turns in the primary and the secondary of a transformer is 1000 and 3000 respectively. If 80-volt a.c. is applied to the primary coil of the transformer, then the potential difference per turn of the secondary coil would be ? 0.08 volt 240 volt 2400 volt 0.24 volt 15. Which of the following devices in their common form would not function on a steady direct current filament lamp electric heating element transformer electric bell 16. An induction coil is generally used to produce a large output voltage rectify an alternating current produce a large input voltage smothen a pulsating direct current 17. The iron core of an induction coil is made from bundles of wires so as to minimize eddy currents get the greatest possible secondary voltage generate eddy currents prevent sparking at the contact breaker 18. As shown in Fig. 4 (CF). 20, P, and Q are two co-axial conducting loops separated by some distance. When the switch S is closed, a clockwise current Ip flows in p ( as seen by E), and an induced current IQ1 flows in P (as seen by E ), and an induced current IQ1 flows in Q. The switch remains closed for a long time. When S is opened, a current IQ2 flows in Q. Then directions of IQ1 and IQ2 (as seen by E) are Both anticlockwise Respectively anticlockwise and clockwise Both clockwise Respectively clockwise and anticlockwise 19. The part of the AC generator that passes the current from the coil to the external circuit is Field magnet Slip rings Brushes Split rings 20. A step-up transformer has a ratio of one to ten. Neglecting slight losses, if 100 W of power go into the primary coil, the power coming from the secondary coil is 1000 W. 10 W. 100 W. 1 W. 21. If the primary of a transformer were connected to a dc power source, the transformer would have a voltage output Only while being connected or disconnected. That is also dc. The same. At a higher efficiency than with an ac source. 22. When a wire loop is related in a magnetic field the direction of included EMF change once in each. ¼ revolution 2 revolution ½ revolution 1 revolution 23. The core of an efficient transformer should consist of laminated pieces of metal in order to increase the heat produced by increasing the eddy current increase the heat produced by reducing the eddy current reduce the heat produced by reducing the eddy current reduce the heat produced by increasing the eddy current 24. Two inductances 4 H and 8 H are arranged in series and a current of 10 A is passed through them. What is the energy stored in them 60 J 600 J 133J 250 J 25. The North pole of a magnet is pushed into a coil, and a current is induced. Which of the following will NOT change the direction of induced current as measured by an ammeter. Pushing the south end of the magnet into the coil Changing the polarity of the ammeter connected to the coil Pulling the North end of the magnet out. Pushing the sound end of the magnet into the coil AND changing the polarity 1 out of 25 Time is Up! Time's up