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प्रश्न
Why and where are eddy currents are undesirable? How are they minimized?
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उत्तर
Undesirable effects of eddy currents:
The soft iron core is used in dynamo transformers, motors, generators, etc. When a.c is passed through these instruments the flux changes and eddy currents are set up in the core. Therefore, the core is heated up so the electrical energy is wasted in the form of heat energy.
Minimization of the undesirable effect of eddy current:
- To minimize the undesirable effect of eddy currents, laminated or insulated iron core is used which minimizes the magnitude of eddy currents.
- If the surface area of the metal plate is reduced, amount of eddy current generated is reduced.
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संबंधित प्रश्न
State any two causes of energy loss in actual transformers.
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Describe briefly three main useful application of eddy currents ?
If the magnetic field outside a copper box is suddenly changed, what happens to the magnetic field inside the box? Such low-resistivity metals are used to form enclosures which shield objects inside them against varying magnetic fields.
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(a) hold the sheet there if the metal is magnetic
(b) hold the sheet there if the metal is nonmagnetic
(c) move the sheet away from the pole with uniform velocity if the metal is magnetic
(d) move the sheet away from the pole with uniform velocity if the metal is nonmagnetic.
Neglect any effect of paramagnetism, diamagnetism and gravity.
Write two examples of their useful applications .
State applications of eddy currents.
Two simple pendula of length L and 4L are pulled aside to the right and are at rest so that they make an angle 30° with the vertical. They are then released simultaneously at time t = 0. The time after which they will be in phase is ______.
If the length of a simple pendulum increases by 5%, then its period shall increase by ______.
For high frequency, capacity offers
Which one is not an application of eddy current?
A metal plate is getting heated. It can be because ______.
- a direct current is passing through the plate.
- it is placed in a time varying magnetic field.
- it is placed in a space varying magnetic field, but does not vary with time.
- a current (either direct or alternating) is passing through the plate.
Consider a metallic pipe with an inner radius of 1 cm. If a cylindrical bar magnet of radius 0.8 cm is dropped through the pipe, it takes more time to come down than it takes for a similar unmagnetised cylindrical iron bar dropped through the metallic pipe. Explain.
