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I am not at all able to understand what are the terms magnetic dip and magnetic declination.Also how will the magnetic dip and magnetic declination change on moving from equator to poles.

Also i am getting confused about the compass needle and how it should be held to measure these quantities at equator and poles.

Kindly explain the concept in detail with respect to the compass needle and its movement,if we move from equator to poles (both dip angle and declination).

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For a typical compass with a magnetic needle

dip is the vertical angle of the needle from a locally horizontal plane. As you approach a magnetic pole the dip increases, the end of the needle is pulled downwards.

declination is the horizontal angle between where the needle points (local magnetic north) and true north (geographic north).

Both these vary considerably from place to place and from year to year.

Variation in Declination

The magnetic north pole wanders around considerably.

enter image description here

At some periods in the past the magnetic north pole has been located near the south pole.

There are also local magnetic anomalies that can affect a compass needle.

So, in conclusion, how a compass needle moves as you travel from equator to pole depends on where you start, when you start, what route you take, how long you take and on which of many north poles you aim to reach.

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  • $\begingroup$ would you please say how declination will change if we move from equator to poles?(from your answer i know that there is no such specific answer.)But is there a general trend for this i.e for change in declination $\endgroup$
    – Abhishek P G
    Commented Feb 26, 2016 at 13:45
  • $\begingroup$ @AbhishekPallipparagopakumar: Examine the declination map above. General trends (if any) should be readily apparent. $\endgroup$
    – RedGrittyBrick
    Commented Feb 26, 2016 at 13:49
  • $\begingroup$ According to my interpretation i find that declination angle increases from equator to poles.But i still doesn't understand its logic.I mean how it keeps on increasing till we reach the pole.What i mean is,since the magnetic meridian do not coincide with the geographic meridian and if we assume it to be tilted by an angle 30 !degree.cyberphysics.co.uk/topics/magnetsm/meridians.gif And then if we move from equator till the magnetic meridian the declination would increase.Then after that if we move from the magnetic meridian to pole it should decrease right? $\endgroup$
    – Abhishek P G
    Commented Feb 26, 2016 at 15:08
  • $\begingroup$ @AbhishekPallipparagopakumar: The magnetic meridian is an imaginary construct and bears little relation to how a magnetic compass needle moves as it travels from equator to poles on the actual surface of the non-imaginary Earth. $\endgroup$
    – RedGrittyBrick
    Commented Feb 26, 2016 at 15:18
  • $\begingroup$ Yup got that.I emphasized on this question because it would come for our final exam.So something should be written.Well the interpretation from the graph would do anyway. $\endgroup$
    – Abhishek P G
    Commented Feb 26, 2016 at 15:41

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