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A magnetic needle is suspended first at the earth’s north magnetic

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A magnetic needle is suspended first at the earth’s north magnetic pole and then at a point on the magnetic equator. The respective angles between the needle and the horizontal are

A. 0° and 0°

B. 60° and 60°

C. 90° and 90°

D. 90° and 0°

QUICK ANSWER…

D

DETAILS…  

To properly answer this question, you will have to recall that:

  • Like poles repel while unlike poles attract.
  • The earth behaves like it has a giant hidden bar magnet whose north pole is slightly aligned to the earth’s geographic north (close to northern Russia), and south pole slightly aligned to the earth’s geographic south (Antarctica, close to Argentina).

If a magnetic needle is suspended freely at the earths north magnetic pole, the hidden giant bar magnet within the earth will communicate with the needle so that the north pole of the needle is repelled while the south pole of the needle is attracted, this leaves the needle standing upright like this: ↓, with north pole upwards and south pole downwards. This arrangement forces the needle to make an angle of 90° with the horizontal.

However, if we move the same needle to the equator, a region located around the middle of the hidden giant bar magnet, the same communication occurs, the north pole of the needle will point towards the south pole of the earth’s giant magnet, while the needle’s south pole will point towards the earth’s north pole. If the needle is observed from the top by the observer, it will lie flat making an angle of 0° with the horizontal.

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Now for the right answer to the above question:

  1. A is not the right answer. it will stand upright, making an angle of 90° with the horizontal.
  2. B is incorrect.
  3. C is incorrect. it will lie flat, making an angle of 0° with the horizontal.
  4. D is correct. 90° at any of the earth’s magnetic poles, and 0° at any point on the equator. Nigeria is located at the equator; you can try this.

KEY-POINTS…

You may please note this/these:

  • Like poles repel.
  • Unlike poles attract.
  • The earth behaves as though is has a giant bar magnet hidden within its crust.
  • The earth’s magnetic north will attract the needles south pole and repel its north pole, making it stand upright as observed by the observer standing on the north pole.
  • The needle will still communicate with the earth’s magnet at the equator, making it lie horizontal.

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/ culled from 2020 JAMB-UTME physics past question 23 /

A magnetic needle is suspended first at the earth’s north magnetic » QuizTablet
A magnetic needle is suspended first at the earth’s north magnetic » QuizTablet

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