Magnetism & Compass Flashcards
Examples of permanent magnetism?
The steel of which ship is built of. Hull, ships structure, bulkheads, cranes, engines, anchors
Examples of electro magnetism?
Added machinery, speakers, instruments
What is variation?
The angular difference between True north and Magnetic north
Which msn is magnetic compasses?
MSN 1631
When should the magnetic compass be adjusted? (5 Factors)
- Every two years the compass must be swung and adjusted by a compass adjuster
- When major yard work has been conducted which may have changed the permanent magnetism
- If new equipment has been added
- Damage has been done to the vessel
- If a noticeable change has been seen
What is deviation?
The angular difference between Magnetic north and Compass north
What are permanent magnets used for?
To counteract ship’s permanent magnetism
How do we counteract Induced magnetism?
Soft Iron
Horizontal magnetism = Kelvin balls
Vertical magnetism = Flinders bar
Which solas chapter and annex is magnetic compasses?
Solas chapter 5. Annex 13
Name some reasons for a change in deviation in the long term? (2 factors)
Refit period. If major works are undertaken causing vibrations to the hull.
Long voyages on repeated heading
Reasons for a change in deviation in the short term? (4 factors)
- Changes of electrical equipment.
2 .Heavy shocks to vessel- pounding. - Lightning strikes
- If lubber line is incorrectly aligned.
What does a fluxgate compass do?
Detects the Earth’s magnetic field electronically.
Advantages of fluxgate compass? (4 factors)
- Small with no moving parts
- Self correcting
- Transmits data to other units.
- Can be fitted anywhere.
Disadvantages of a fluxgate compass? (2 factors)
- Must remain horizontal so must be fitted with gimbals/ additional vertical correctors.
- Requires power to drive the reference coils.
What is induced magnetism?
The short temporary effect on the compass due the heading or temporary changes due to i.e cargo
What is a Petal diagram?
