Which of the following statements is/are true regarding the isogonic lines? i. They converge at the magnetic poles. ii. They are equally spaced everywhere on Earth. iii. They run parallel to the equator. iv. They do not change position over time.
- AOnly (i)Correct
- BOnly (i) and (ii)
- COnly (iii) and (iv)
- D(i), (ii), (iii) and (iv)
Solution
Concept
Properties and characteristics of isogonic lines
Formula
NONE
Step-by-step solution
1. Isogonic lines are lines drawn on a map connecting points of equal magnetic declination. 2. Because magnetic meridians meet at the magnetic poles, all isogonic lines converge at the magnetic poles. 3. Isogonic lines do not remain static, parallel, or equally spaced, making statements ii, iii, and iv incorrect. Answer: A
Explanation
Isogonic lines are lines drawn on a map connecting points on the Earth's surface that share the same magnetic declination. Because magnetic field lines originate and terminate at the magnetic poles, all isogonic lines naturally converge at these locations. Since they are neither equally spaced, parallel to the equator, nor static over time, option A is the only correct statement.
Why the other options are wrong
B) Isogonic lines are not equally spaced everywhere on Earth due to irregular magnetic field variations. C) Isogonic lines do not run parallel to the equator and they change position over time due to secular variation. D) Statements (ii), (iii), and (iv) are false regarding the characteristics of isogonic lines.
Shortcut
Isogonic lines = Lines of equal declination that only converge at magnetic poles.
Common mistake
Selecting Option B by assuming isogonic lines are uniformly spaced across the Earth's surface like latitude lines.
Correct answer: A) Only (i)