The direction of magnetic field at any location on the earth's surface is commonly specified in terms of
- A.field declination
- B.field inclination
- C.both field declination and field inclination
- D.horizontal component of the field
Correct answer
Explanation
The correct answer is C, both field declination and field inclination. A direction in space needs two angles, one in the horizontal plane and one in the vertical plane, and declination and inclination supply exactly these.
Declination is the angle between the magnetic meridian and the geographic meridian at a place, so it tells how far a compass needle points away from true north. Inclination, also called dip, is the angle the Earth's field makes with the horizontal; a freely suspended needle is horizontal at the magnetic equator and vertical (90 degrees) at the magnetic poles. Together with the horizontal component, these are the three magnetic elements of the Earth, but the direction alone is fixed by the two angles.
A is wrong because declination gives only the horizontal bearing, not the tilt. B is wrong because inclination gives only the tilt, not the bearing. D is wrong because the horizontal component is a strength, not a direction.
Exam tip: three elements of Earth's magnetism = declination, dip (inclination) and horizontal component; dip is 0 at the magnetic equator and 90 degrees at the poles.
Practice Questions
View allThe fact that the planets move around the Sun, not in circles but in ellipses, was first demonstrated by
- A.Galileo
- B.Martin Luther
- C.Johannes Kepler
- D.Copernicus
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In 1609 Kepler showed that the planets move around the Sun in elliptical orbits, with the Sun at one focus of the ellipse.
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- C.Urea is produced from digestion of starch.
- D.Urea is produced in lung and kidney.
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- B.Objective lens-Condenser-Body tube-Eyepiece
- C.Condenser-Objective lens-Body tube-Eyepiece
- D.Eyepiece-Objective lens-Body tube-Mirror
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- D.Haemoglobin is only used for blood clotting and not for carrying gases.
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- B.Histones are proteins that are present in nucleus in association with DNA.
- C.Histones are proteins associated with lipids in the cytosol.
- D.Histones are proteins associated with carbohydrates in the cytosol.
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