The following are different factors that affect the diurnal variation in magnetic declination. The condition which may result in the maximum variation is:
- Aat the Equator during summer
- Bat the Magnetic Poles during summerCorrect
- Cat the Equator during winter
- Dat the Magnetic Poles during winter
Solution
Concept
Diurnal variation of declination is larger near the magnetic poles than at the equator, and larger in summer than in winter.
Step-by-step solution
1. Diurnal variation is the daily swing of the magnetic needle. 2. It increases as we go towards the magnetic poles and is less near the equator. 3. It is more in summer than in winter. 4. It is also more in day time than at night. 5. So the maximum variation is at the magnetic poles during summer.
Explanation
The daily change in magnetic declination is not the same everywhere. It is larger near the magnetic poles and smaller near the equator. It is also larger in summer than in winter, so the poles in summer give the maximum.
Why the other options are wrong
A: Equator gives less variation than the poles. C: Equator in winter gives the least variation. D: Winter gives less variation than summer.
Shortcut
Max diurnal variation = Poles + Summer + Day; Min = Equator + Winter + Night.
Common mistake
Thinking the equator gives more variation because of stronger sunlight there.
Correct answer: B) at the Magnetic Poles during summer