1) How can you explain that Lenz's law does not violate the law of conservation of energy?
[asked by: Neeraj Pandit]
neetpcb Answer: Lenz's law does not violate the law of conservation of energy. It is due to the fact that, had the direction of induced current been opposite to that given by Lenz's law, with a slight push to a magnet towards the coil, the magnet would be automatically pulled in [unlike magnetic poles attract each other], causing more and more change of linked flux. This would mean production of current without doing any work. This would have violated the Law of Conservation of Energy as energy cannot be produced from nothing. The actual case in practise is that mechanical work is spent in overcoming the opposing force given by the coil to the change of flux, which in turn gets converted into emf, before ultimately being dissipated as Joule heating. So, Lenz's Law does not violate the Law of Conservation of Energy.
2) What is non-inductive winding?
[asked by: Abhishek Das]
neetpcb Answer: Non-inductive winding of a coil is that kind of wiring in which no part of the coil suffers any self-inductance. It is made by making the coil of a double-helix pattern in which each pair of consecutive current-carrying wires carry current in opposite direction, thus cancelling the induction due to one-another.
3) What is the induced emf between the wheels of a train moving with a velocity of 108 kmph is the length of its axle is 2 m?[Earth's magnetic field = 0.00008T, parallel to the velocity of the train]
[asked by: Rahul Sharma]
neetpcb Answer: The induced emf due to motion is given by E = B(LxV)
Now, velocity of the train = 108*1000/3600 = 30m/s
Therefore, emf = 0.00008(2*30*Sin 90) = 0.0048 V
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