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प्रश्न
The earth’s magnetic field varies from point to point in space. Does it also change with time? If so, on what time scale does it change appreciably?
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उत्तर
Earth’s magnetic field changes with time. It takes a few hundred years to change by an appreciable amount. The variation in the earth’s magnetic field with time cannot be neglected.
संबंधित प्रश्न
A compass needle, free to turn in a vertical plane orients itself with its axis vertical at a certain place on the earth. Find out the values of (i) horizontal component of earth's magnetic field and (ii) angle of dip at the place.
Name the electromagnetic waves which (i) maintain the Earth’s warmth and (ii) are used in aircraft navigation.
What is the angle of dip at a place where the horizontal and vertical components of the Earth’s magnetic field are equal?
Where on the surface of Earth is the angle of dip zero?
A horizontal straight wire of length L extending from east to west is falling with speed v at right angles to the horizontal component of Earth’s magnetic field B.
(i) Write the expression for the instantaneous value of the e.m.f. induced in the wire.
(ii) What is the direction of the e.m.f.?
(iii) Which end of the wire is at the higher potential?
Can the earth's magnetic field be vertical at a place? What will happen to a freely suspended magnet at such a place? What is the value of dip here?
Answer the following question in detail.
How does the magnetic declination vary with latitude? Where is it minimum?
What happens to the angle of dip as we move towards magnetic pole from magnetic equator?
Answer the following question regarding earth’s magnetism:
The angle of dip at a location in southern India is about 18°. Would you expect a greater or smaller dip angle in Britain?
Answer the following question regarding earth’s magnetism:
In which direction would a compass free to move in the vertical plane point to, if located right on the geomagnetic north or south pole?
Answer the following question regarding earth’s magnetism:
The earth’s field, it is claimed, roughly approximates the field due to a dipole of magnetic moment 8 × 1022 J T−1 located at its centre. Check the order of magnitude of this number in some way.
Answer the following question regarding earth’s magnetism:
Geologists claim that besides the main magnetic N-S poles, there are several local poles on the earth’s surface oriented in different directions. How is such a thing possible at all?
The earth may have even reversed the direction of its field several times during its history of 4 to 5 billion years. How can geologists know about the earth’s field in such distant past?
At a certain location in Africa, a compass points 12° west of the geographic north. The north tip of the magnetic needle of a dip circle placed in the plane of magnetic meridian points 60° above the horizontal. The horizontal component of the earth’s field is measured to be 0.16 G. Specify the direction and magnitude of the earth’s field at the location.
A long straight horizontal cable carries a current of 2.5 A in the direction 10° south of west to 10° north of east. The magnetic meridian of the place happens to be 10° west of the geographic meridian. The earth’s magnetic field at the location is 0.33 G, and the angle of dip is zero. Locate the line of neutral points (ignore the thickness of the cable)? (At neutral points, magnetic field due to a current-carrying cable is equal and opposite to the horizontal component of earth’s magnetic field.)
Which of the following is responsible for the earth’s magnetic field?
The vertical component of earth’s magnetic field at a place is √3 times the horizontal component the value of angle of dip at this place is ______.
The net magnetic flux through any closed surface, kept in a magnetic field is ______.
The small angle between magnetic axis and geographic axis at a place is ______.
Assume the dipole model for earth’s magnetic field B which is given by BV = vertical component of magnetic field = `mu_0/(4pi) (2m cos theta)/r^3` BH = Horizontal component of magnetic field = `mu_0/(4pi) (sin theta m)/r^3` θ = 90° – lattitude as measured from magnetic equator. Find loci of points for which (i) |B| is minimum; (ii) dip angle is zero and (iii) dip angle is ± 45°.
