Applied Electricity Paper 2 , Nov/Dec. 2011  
Questions:   1 2 3 4 5 6   Main
General Comments

Question 2

  1.  Explain briefly how an e.m.f. is induced in a conductor cutting magnetic flux.
  2.  If an e.m.f. of 6 V is induced in a coil when the current in an adjacent coil  varies at a rate of 92 A/s, calculate the value of the mutual inductance.





The expected answers were:

  1. When a conductor (e.g. a wire) is moved through a magnetic field in such a way that it cuts the magnetic lines of force (i.e. magnetic flux), a voltage is induced in the conductor. An electric current will flow through the conductor if the two ends of the conductor are connected by a wire to form a circuit. Suppose the conductor has a length L metres and moves perpendicularly to the lines of flux in a uniform magnetic field of B tesla at a velocity of V metre per sec., then, in one second, the flux cut,

E = Blv volts

  1. vL = L

L(mutual inductance) =
                               =   = 65.22 mH
The question was on Electromagnetic Field. The question was unpopular with the candidates. The candidates were reported to show little knowledge of this topic.



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