A geographical grid has : 1. Lines that run east to west around the globe to mark latitude 2. Lines that run north to south from north pole to south pole indicate longitude Which of the statements given above is/are correct ?
- (a)1 only
- (b)2 only
- (c)Both 1 and 2
- (d)Neither 1 nor 2
Correct — C, both 1 and 2. Statement 1 is right — a parallel of latitude runs east to west and draws a complete circle around the Earth, the Equator being the largest circle and the parallels shrinking as you move towards either pole. Statement 2 is right as well — a meridian of longitude runs north to south, and each one is a half-circle joining the North Pole to the South Pole. Taken together these two sets of lines are precisely what is meant by a geographical grid; the school text calls them grid lines and says that all these lines together constitute a grid for the globe.
- (a)1 only — This rejects statement 2, but statement 2 is correct as written — meridians of longitude do run from the North Pole to the South Pole, each of them a half-circle.
- (b)2 only — This rejects statement 1, but statement 1 is correct as written — parallels of latitude do run east to west, each closing into a circle around the globe.
- (d)Neither 1 nor 2 — Both statements are correct, so rejecting both is doubly wrong. This option only works if you have swapped the two sets of lines in memory.
A geographical grid is the reference frame that makes a place addressable. Parallels of latitude measure how far north or south of the Equator you are and run as complete circles; meridians of longitude measure how far east or west of the Prime Meridian you are and run as half-circles from pole to pole. A latitude and a longitude together fix one point on the Earth's surface and nowhere else.
Almost every wrong answer on this item comes from swapping the two sets. The picture to fix is a cage — the parallels are the horizontal rungs, unequal in length and shrinking towards the poles, while the meridians are the vertical bars, all of equal length and all converging at the poles. From that picture two exam favourites follow for free — the Equator is the longest parallel and also the only parallel that is a great circle, and the distance between two meridians is greatest at the Equator and falls to zero at each pole. Note also that the answer does not depend on the awkward phrasing of the statements; both describe the standard grid correctly.
- A parallel of latitude draws a circle around the Earth; the Equator at 0 degrees is the largest, and the circles grow smaller towards the poles.
- Meridians of longitude are all half-circles running from one pole to the other, and they are all of the same length.
- The Prime Meridian through Greenwich was adopted as the international standard in 1884 and is marked as 0 degrees longitude.
- Longitude is counted 0 to 180 degrees east and 0 to 180 degrees west, and 180 degrees east and 180 degrees west are the same line.
Both statements describe their own set correctly, so the answer is (c) Both 1 and 2.
- Swapping the two sets — remembering that parallels are the horizontal rungs of the cage fixes it.
- Believing meridians are full circles; each meridian is a half-circle, completed only by its opposite.
As a two-statement item like this one, as ‘which is the longest parallel’, or through the time difference between two longitudes.
Consider the following statements : 1. Distance between the longitudes becomes zero on North Pole and South Pole. 2. Distance between the longitudes is maximum on the Equator. 3. Number of longitudes is more than number of latitudes. Which of the statements given above is/are correct ?
- (a) 1 only
- (b) 2 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer(d) 1, 2 and 3
The same grid, tested for its geometry rather than its definition, in the session before this one. Once you picture meridians as half-circles converging at the poles, both items answer themselves.
Which one of the following is the longest parallel of latitude?
- (a) Tropic of Cancer
- (b) Tropic of Capricorn
- (c) Arctic Circle
- (d) Equator
Answer(d) Equator
The consequence of statement 1 here. Parallels are circles of unequal size and the Equator is the largest of them, which is the single most repeated fact about the grid in NDA papers.
- practice — not a real PYQ
Which one of the following is the longest parallel of latitude?
- (a)Tropic of Cancer
- (b)Arctic Circle
- (c)Equator
- (d)Tropic of Capricorn
Answer(c) Equator — parallels shrink steadily from the Equator towards each pole.
- practice — not a real PYQ
Meridians of longitude are best described as
- (a)full circles of equal length
- (b)half-circles running from pole to pole
- (c)circles that grow smaller towards the poles
- (d)lines drawn parallel to the Equator
Answer(b) half-circles running from pole to pole — all of them of the same length, meeting at both poles.