What is eddy current ? Mention its uses.
ans:
Eddy currents are called Foucault currents. They are loops of electrical current induced within conductors by a changing magnetic field in the conductor, due to Faraday's law of induction.
It's uses are as follows:
i) Induction Heating
ii) Energy meters
iii) Electromagnetic brakes
2.
What are Faradys laws of electromagnetic induction ?
ans:
Michael Faraday in 1831 , an English physicist gave one of the most basic laws of electromagnetism called Faraday's law of electromagnetic induction.
Laws of electro magnetic induction are as follows:
i) When magnetic flux linking with conductor is changed emf is induced
ii)Induced emf lasts so long as the the magnetic flux linkage changes continously.
iii)Magnitude of induced emf is equal to rate of change of flux linkage.
3.
Why power lines are transmitted in high voltage in long distances ?
ans:
4.
Can dc be used in a transformer ?
ans:
5.
What is the use of soft iron core in a transformer ?
ans:
6.
What is Lenzs law ?
ans:
Lenz’s law states that the emf is induced to send an induced current in such a direction as to oppose the causes which produce it.
(You can get the reference from one of my earlier post)
7.
. Show that Lentz law is in accordance with law of conservation of energy .
ans:
8. What are losses in a transformer ?
ans:
i) Copper losses
ii) Flux losses
iii) Iron losses
iv) Losses due to vibration of core.
12. A coil of area 50cm2 is perpendicular to a uniform field of flux density 10-3wbm-2(T).(i) what is the flux passing through the coil?
ans:
14. A magnet falls through a metal ring . Will the acceleration of the magnet be less than g , equal to g or more than g ?
ans:
No , acceleration of magnet will be less than ‘g ‘ . This is because as magnet falls amount of magnetic flux linked with the ring changes . An induced current is developed in the ring which opposes the downward motion of the magnet .After the magnet has crossed the metal ring , amount of magnetic flux linked with the ring goes on decreasing . An induced current is developed in the ring and opposes the fall of magnet . Therefore downward acceleration of magnet continues to be less than ‘ g ’
due to this the acceleration goes on decreasing
15.
What is self induction
ans:
The process of inducing emf in a coil due to the flow of current through itself is called self induction.
The coefficient of self induction of a coil is defined as the property of the coil by virtue of which it opposes the change in current flowing through it.
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