Electromagnetic Induction and Alternating Current


A boat is moving due east in a region where the earth's magnetic field is 5.0 × 10-5 NA-1m-1 due north and horizontal. The boat carries a vertical aerial 2m long. If the speed of the boat is 1.50 ms-1, the magnitude of the induced emf is

  1. 0.15 mV
  2. 0.50 mV
  3. 0.75 mV
  4. 1 mV
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A resistor 'R' and 2μF capacitor in series is connected through a switch to 20 V direct supply. Across the capacitor is a neon bulb that lights up at 120 V. Calculate the value of R to make the bulb light up 5s after the switch has been closed. (log102.5 = 0.4)

  1. 2.7 x 106 Ω
  2. 1.3 x 104 Ω
  3. 1.7 x 105 Ω
  4. 3.3 x 107 Ω
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If an ammeter is to be used in place of a voltmeter, then we must connect with the ammeter a

  1. low resistance in series
  2. high resistance in series
  3. low resistance in parallel
  4. high resistance in parallel
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A wire when connected to 220 V mains supply has power dissipation P1. Now the wire is cut into two equal pieces which are connected in parallel to the same supply. Power dissipation in this case is P2. Then P2:P1 is

  1. 1
  2. 2
  3. 3
  4. 4
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An arc lamp requires a direct current of 10 A and 80 V to function. If it is connected to a 220 V (rms), 50 Hz AC supply, the series inductor needed for it to work is close to:

  1. 0.08 H
  2. 0.044 H
  3. 0.065 H
  4. 80 H
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