单项选择题
When crossing the magnetic equator the（）.
A.Flinders bar should be inverted
B.Heeling magnet should be inverted
C.The quadrantal spheres should be rotated 180°
D.Flinders bar should be moved to the opposite side of the binnacle
相关考题
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单项选择题
What is used to correct for both induced and permanent magnetism，and consequently must be readjusted with radical changes in latitude（）.
A.Flinders bar
B.Soft iron spheres
C.Fore-and-aft permanent magnets in their trays
D.Heeling magnet -
单项选择题
What is the basic principle of the magnetic compass（）.
A.Magnetic materials of the same polarity repel each other and those of opposite polarity attract
B.The Earth's magnetic lines of force are parallel to the surface of the Earth
C.Magnetic meridians connect points of equal magnetic variation
D.The compass needle（s）will，when properly compensated，lie parallel to the isogonic lines of the Earth -
单项选择题
Variation in a compass is caused by（）.
A.Worn gears in the compass housing
B.Magnetism from the earth's magnetic field
C.Magnetism within the vessel
D.Lack of oil in the compass bearings
