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प्रश्न
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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उत्तर
The varying magnetic field induces eddy currents on the walls of the copper box. There is a magnetic field due to the induced eddy currents, that is in opposite direction. As copper has good conductivity, thus the magnetic field due to the eddy currents will be strong. The magnetic field induced due to eddy currents in the copper walls cancel the original magnetic field. Thus, magnetic field does not penetrate the enclosure made of copper. The magnetic field inside the box remains zero. This is how a copper box protects the inside material from varying magnetic fields.
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संबंधित प्रश्न
Give one example of use of eddy currents.
A metallic bob A oscillates through the space between the poles of an electromagnet (See the figure). The oscillations are more quickly damped when the circuit is on, as compared to the case when the circuit is off. Explain.
A metal sheet is placed in front of a strong magnetic pole. A force is needed to ______________ .
(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.
How are eddy currents generated in a conductor which is subjected to a magnetic field?
Write two examples of their useful applications .
How can the disadvantages of eddy currents be minimized?
Give the uses of Foucault current.
The plane in which eddy currents are produced in a conductor is inclined to the plane of the magnetic field at an angle equal to ______.
Identify the wrong statement.
If the length of a simple pendulum increases by 5%, then its period shall increase by ______.
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Which one is not an application of eddy current?
