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. The core of an efficient transformer should consist of laminated pieces of metal in order toincrease the heat produced by reducing the eddy currentincrease the heat produced by increasing the eddy currentreduce the heat produced by increasing the eddy currentreduce the heat produced by reducing the eddy current2. Metal detectors, like the ones used at airports, are activated by Electric fields.Alternating current.Electromagnetic induction.Magnetic fields.3. Lenz's law is a law of the conservation ofElectric chargeElectric currentMomentumEnergy4. In an AC circuit the applied emfÂ e = Eo sin (Ï‰t + Ï€/2)Â leads the currentÂ I = Io sin (Ï‰t â€“ Ï€/2)Â by Ï€/2Ï€0Ï€/45. The efficiency of a transformer can be increased ifhigh resistance copper coils are usedthe core is designed to increase eddy currentsthe core is made of soft magnetic materials thereby reducing the energy for magnetic reversals6. The power loss is less in transmission lines whenVoltage is less but current is moreBoth voltage and current are lessVoltage is more but current is lessBoth voltage and current are more7. If two inductors of inductances 3H and 6H are arranged in series, the total inductance is2.0 H9.0 H0.5 H18.0 H8. The iron core of an induction coil is made from bundles of wires so as toget the greatest possible secondary voltageprevent sparking at the contact breakergenerate eddy currentsminimize eddy currents9. A dynamo primarily convertspotential energy into kinetic energykinetic energy into potential energymechanical energy into electrical energyelectrical energy into mechanical energy10. On an ac generator which of the following does not apply ?commutatorslip ringsarmaturefield magnet11. Which of the following devices may be used to step up the voltage in a dc circuit?a step up transformeran induction coila wattmetera dc generator12. A 10 V battery of negligible internal resistance is switched across a coil of 1H inductance and 40 ohm resistance Find the initial current0.25 A1.25 A0 A1 A13. A coil of area of cross section withÂ 10Â turns is in a plane which is perpendicular to an uniform magnetic field of The flux though the coil isZero1 Wb100 Wb10 Wb14. A coil of 2H AND 10Î© resistance is connected to a 20V dc supply. CalculateÂ the final steady current0.2 A0.5 A5 A2 A15. The best material for the core of the primary and secondary coils of an induction coil isrubbersoft ironcopper,steel16. Compared to the primary voltage, the secondary voltage may beLarger, smaller, or the same.The same.Smaller.The same or smaller, but not larger.17. Which of the following statements about magnetic fields,Â is not true? Magnetic fields are regions in which magnetic forces can be detected.Magnetic field strength increases as the distance from the magnetic source increases.Magnetic fields are vector quantities.Magnetic fields have both magnitude and direction.18. The unit henry can also be written as (3)(4)(1)(2)19. 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 1 W.100 W.1000 W.10 W.20. A magnet is placed into a coil. Â The induced EMF across the coil is 10mV. Â What would the EMF be if the coil was replaced by a coil with twice as many coils, and the passage of the magnet into the coil took twice as long.0mV10mV20mV5mV21. 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 coil2.500 A1.600 A6.250 A0.625 A22. A 10 V battery of negligible internal resistance is switched across a coil of 1H inductance and 40 ohm resistance Find the final current1 A1.25 A0 A0.25 A23. A coil of 4H and resistance 2 ohms carries a steady current of 2A. Calculate the energy stored1J8J4J3J24. 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 ? 0.24 volt2400 volt240 volt0.08 volt25. The magnetic flux linked with the coil varies with time as Â = 3 t^{2} +4t + 9. The magnitude of induced EMF at t = 2 s is ? 9 V16 V4 V3 V26 out of 25Time is Up!