Variation is a compass error that you（）.

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

单项选择题True heading differs from magnetic heading by（）.

A.deviation
B.variation
C.compass error
D.northerly error

单项选择题To center a compass bowl in its binnacle，you should have the ship on an even keel，heading north or south，and adjust the screws until（）.

A.the compass heading is in line with the lubber's line
B.there is no lost motion in the gimbal rings
C.no change of heading by compass is observed if you raise and lower the heeling magnet
D.the gimbal rings do not strike the compass frame when they are tilted

单项选择题The vertical component of the Earth’s magnetic field causes induced magnetism in vertical soft iron. This changes with latitude. What corrects for this coefficient of the deviation? （）

A.The Flinders bar
B.The heeling magnet
C.Quadrantal soft iron spheres
D.Bar magnets in the binnacle

单项选择题The vertical angle between the horizontal and the magnetic line of force is the（）.

A.elevation
B.magnetic angle
C.vertical angle
D.dip