Magnetism

Question 1

Examples of permanent magnetism?

Answer 1

The heading the ship is built on. Hull, ships structure, bulkheads, cranes

Question 2

Examples of induced iron?

Answer 2

Machinery added, speakers, instruments

Question 3

What is variation?

Answer 3

Difference between true north and magnetic north

Question 4

Which msn is magnetic compasses?

Answer 4

MSN 1631

Question 5

Name 8 reasons when the magnetic compass should be adjusted

Answer 5

1- when first installed

2- becomes unreliable

3- changes to ships magnetic field

4-magnetic equipment is added or removed

5- deviation has not been maintained

6- collision

7- change of latitude

8- every watch

Question 6

What is deviation?

Answer 6

Is the amount by which the ships compass is altered due to ships iron

-the angle between the magnetic meridian and the direction the needle is actually pointing= deviation.

-if compass north lies to the east of the magnetic meridian, the deviation is said to be easterly. If west, westerly.

Question 7

What are permanent magnets used for?

Answer 7

Are used to counteract permanent ship magnetism.
You have : longitudinal magnetism and athwart ships magnetism

Question 8

Soft iron is used to counteract magnetism. Which iron counteracts the horizontal magnetism?
Which iron counteracts the vertical magnetism?

Answer 8

-horizontal = kelvin balls
-vertical = flinders bar

Question 9

Which solas chapter and annex is magnetic compasses?

Answer 9

Solas chapter 5. Annex 13

Question 10

Name some reasons for a change in deviation in the long term?

Answer 10

-refit period. If major works are undertaken causing vibrations to the hull.
-long voyages on repeated heading.

Question 11

Reasons for a change in deviation in the short term?

Answer 11

-changes of electrical equipment.
-heavy shocks to vessel- pounding.
-lightening strikes
-if lubber line is incorrectly aligned.

Question 12

What does a fluxgate compass do?

Answer 12

Fluxgate compass utilises the earths magnetic field and the properties of electromagnetic actions.

Question 13

Advantages of fluxgate compass?

Answer 13

-small with no moving parts
-self correcting
-transmits data to other units.
-can be fitted anywhere.

Question 14

Disadvantages of a fluxgate compass?

Answer 14

-Must remain horizontal so must be fitted with gimbals/ additional vertical correctors.
-requires power to drive the reference coils.