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Magnetism and Matter — Physics STD 12 Science — Question

Gujarat BoardEnglish MediumSTD 12 SciencePhysicsMagnetism and Matter4 Marks
Question
Mention the changes occurring in the geomagnetic components.
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Answer

Changes in the geomagnetic components : Magnitudes of geomagnetic components are not only different at different places on the earth and there are usual and unusual changes in their magnitudes at same place also. These changes are as follows:
(1) Long term changes: According to Kelvin, changes in magnitudes of geomagnetic components occur very slowly with time and after one thousand years, they again come back to their original value. According to him, the cause of this change is the spinning of magnetic poles around the geographic poles.
(2) Annual changes: These changes complete their cycle in one year. These changes are maximum in a particular month and minimum in another particular month and their characteristics is of opposite types in both hemispheres. For example, in the month of February, angle of dip is maximum in northern hemisphere and minimum in southern hemisphere. In contract to this, in the month of August, it is minimum in northern hemisphere and maximum in southern hemisphere.
(3) Daily changes : In magnitude of geomagnetic elements, there are daily changes. These changes are maximum at a particular time of the day and minimum at another particular time of the day. This time is different for three components.
(4) Non-periodic changes : Sometimes there are sudden changes in geomagnetic components which are known as magnetic disturbance. Whenever black spot in the sun is towards earth, then there is sudden change in geomagnetic elements.

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