Compasses and the magnetic Earth

Tests: 7 of 11 right · Exam: 0 of 4 right · Kind: ★ · Understood: 7 of 15 · Run: 2026-10-18, commit f3c23ea72

Lesson 30 of the physics course of Mova's primary school, as Mova's small model took its tests: it had read this lesson and the ones before it and learned from their exercises. Each test shows the options in the order the student saw them, its choice, the right answer, the score of every option and why it chose. The lesson itself, sentence by sentence with trees and pragmatics: the lesson in the corpora.

Every question of this lesson and each of its options parsed by Mova, with trees and pragmatics: the lesson's questions in the corpora.

Test 1 · ★ · wrong ✗

bro my compass is broken, it's pointing at my phone case magnet lol. is it?

1. Yes, it needs new batteries — ← Mova's choice · score 8
2. Yes, compasses can only break that way — no support
3. No, your phone case is actually north — no support
4. Not broken, the close magnet just pulls harder than the Earth — ✓ the right answer · score 5

Why: It took the question to ask which statement is true. It chose option 1 with score 8, against 5 for the next best. Its support: lesson 30, line 14: «A hiker lines up a map with a compass to choose the right path; a compass needs no batteries or phone signal.», reached through the option's own match among the sentences about the question's things. What matched: the same action «need» (+3); the same thing acted on «batteries» (+3); the same doer «compass» (+2). The right option, 4, scored 5. · the question and its options parsed, with trees and pragmatics

Test 2 · ★ · right ✓

Ollie says a compass points straight to the North Pole. What's the more exact truth?

1. He is exactly right, every time — no support
2. It points to magnetic north, which is a little way off — ← Mova's choice · ✓ the right answer · score 5
3. It points to whichever way you happen to be walking at the time — no support
4. It points to the Sun at midday — no support

Why: It took the question to ask what it is done to. It chose option 2 with score 5, the only option with support. Its support: lesson 30, line 3: «The compass points to the magnetic north, which is not quite the same place as the North Pole at the top of the globe.», reached through the remembered sentence the question matched. What matched: the same receiver «magnetic north» (+4); the same action «point» (+3). Against it: a different doer (counts against) (-2). · the question and its options parsed, with trees and pragmatics

Test 3 · ★ · wrong ✗

In a cartoon, sailors use a compass made of a wooden stick. What's wrong?

1. Wood is too heavy to float on water — ← Mova's choice · score 2
2. Nothing, any wooden stick will point north if it floats — score 1
3. Sticks only point south — no support
4. The needle must be a magnet, and wood is not magnetic — ✓ the right answer · no support

Why: It took the question to ask which statement is true. It chose option 1 with score 2, against 1 for the next best. Its support: lesson 30, line 9: «A magnetised needle on a leaf floating in water turns to point north; sailors used compasses like this nearly a thousand years ago.», reached through the same lesson line as the sentence the question matched. What matched: the same place «water» (+2); the same action «float» (+1). Against it: a different doer (counts against) (-1). The right option, 4, found no support in what it remembers. · the question and its options parsed, with trees and pragmatics

Test 4 · ★ · wrong ✗

What would happen to a compass on a ship made of steel if nobody corrected for it?

1. It would work better than on land — ← Mova's choice · no support
2. It would spin round and round forever and never settle down — no support
3. It could point the wrong way because of the ship's iron — ✓ the right answer · no support
4. It would point at the Moon — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 5 · ★ · right ✓

Granny saw the northern lights from Scotland. What made them?

1. Big city lights reflected by clouds — no support
2. Lightning far away over the sea — score 1
3. Charged bits from the Sun hitting the high air near the poles — ← Mova's choice · ✓ the right answer · score 8
4. Sunlight bouncing off the Arctic ice — no support

Why: It took the question to ask who or what does it. It chose option 3 with score 8, against 1 for the next best. Its support: lesson 30, line 5: «The Earth's magnetic field also guides charged bits from the Sun down near the poles, where they make the air glow as the northern lights, and many birds can f…», reached through the remembered sentence the question matched. What matched: it fills the role the question asks for (+6); the same doer «bits» (+4). Against it: a different thing acted on (counts against) (-2). · the question and its options parsed, with trees and pragmatics

Test 6 · ★ · right ✓

If the Earth had no magnetic field, what might happen over a very long time?

1. Compasses would point south instead — no support
2. Rain would fall upwards — no support
3. The Earth would stop going round the Sun and drift off into space — no support
4. The Sun's charged bits would strip away some of our air — ← Mova's choice · ✓ the right answer · score 2

Why: It took the question to ask which statement is true. It chose option 4 with score 2, the only option with support. Its support: lesson 30, line 12: «Northern lights happen when charged bits from the Sun are guided by the Earth's magnetism down near the poles and make the high air glow; elsewhere the field s…», reached through the same lesson line as the sentence the question matched. What matched: the same thing acted on «some» (+2); the same action «strip away» (+1). Against it: a different doer (counts against) (-1). · the question and its options parsed, with trees and pragmatics

Test 7 · ★ · right ✓

Why might a racing pigeon get confused over a big lump of magnetic iron ore?

1. It uses the Earth's magnetic field to steer, and that can be disturbed — ← Mova's choice · ✓ the right answer · no support
2. Pigeons are scared of rocks — no support
3. The rocks block the smell of home — no support
4. Pigeons only follow motorways — no support

Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 8 · ★ · right ✓

Dad says the Earth is a magnet because there's a giant magnet stone at the North Pole. True?

1. No, it comes from liquid iron moving deep in the core — ← Mova's choice · ✓ the right answer · no support
2. Yes, it is under the ice at the South Pole — no support
3. No, it is the Moon's pull that makes the whole Earth magnetic — no support
4. Yes, a huge magnet rock sits there — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 9 · ★ · wrong ✗

shut up, my mum's going in the MRI with her earrings, so what?

1. Fine, earrings are too small to matter — ← Mova's choice · no support
2. She needs to wear more metal so the machine can see her better — no support
3. Fine, the magnet is switched off for women — no support
4. She must take them off; the huge magnet pulls metal hard — ✓ the right answer · no support

Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Test 10 · ★ · right ✓

Why could you still find your way with a compass if your phone died in the hills?

1. The hills recharge the compass as you walk — no support
2. A compass needs no batteries or signal — ← Mova's choice · ✓ the right answer · score 7
3. A compass can also charge up a dead phone — no support
4. The compass talks to satellites in space — no support

Why: It took the question to ask why something happens (its cause). It chose option 2 with score 7, the only option with support. Its support: lesson 30, line 14: «A hiker lines up a map with a compass to choose the right path; a compass needs no batteries or phone signal.», reached through the option's own match among the sentences about the question's things. What matched: the same doer «compass» (+3); the same action «need» (+2); the same thing acted on «batteries» (+2). · the question and its options parsed, with trees and pragmatics

Test 11 · ★ · right ✓

Which old discovery was first used by sailors nearly a thousand years ago?

1. The radio weather forecast read out for ships at sea — no support
2. Satellite navigation worked out on a mobile phone — no support
3. A battery-powered torch for signalling to other ships — no support
4. A magnetised needle floating to point north — ← Mova's choice · ✓ the right answer · score 5

Why: It took the question to ask what it is done to. It chose option 4 with score 5, the only option with support. Its support: lesson 30, line 9: «A magnetised needle on a leaf floating in water turns to point north; sailors used compasses like this nearly a thousand years ago.», reached through the same lesson line as the sentence the question matched. What matched: the same action «point» (+2); the same doer «magnetised needle» (+2); the same property (+1). · the question and its options parsed, with trees and pragmatics

Exam question 1 · formal language · wrong ✗

Identify the origin of the magnetic field of the Earth.

1. The gravitational attraction of the Moon — ← Mova's choice · no support
2. The motion of molten iron within the outer core — ✓ the right answer · no support
3. A permanent bar magnet situated at the North Pole — no support
4. The accumulation of ice at the polar regions — no support

Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 2 · formal language · wrong ✗

Ascertain the reason for which a compass ought not to be employed in proximity to a steel object.

1. The steel reverses the direction of the Earth's rotation — ← Mova's choice · no support
2. The steel renders the needle too heavy to rotate — no support
3. The steel exerts a stronger influence upon the needle than the Earth — ✓ the right answer · no support
4. The steel deprives the compass of the electrical supply upon which it depends — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 3 · formal language · wrong ✗

Which of the following statements most accurately characterises the direction indicated by a compass needle?

1. The geographic North Pole precisely and without exception — ← Mova's choice · no support
2. Magnetic north, which differs somewhat from the geographic North Pole — ✓ the right answer · no support
3. The position of the Pole Star at all hours — no support
4. The direction in which the observer is facing — no support

Why: No option found support in what it remembers, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

Exam question 4 · formal language · wrong ✗

Select the response consistent with the established facts concerning the aurora.

1. Distant lightning illuminates the night sky — ← Mova's choice · no support
2. Moonlight is reflected from the polar ice upon the clouds — no support
3. Charged particles from the Sun are guided towards the poles and cause the upper air to glow — ✓ the right answer · no support
4. The cold polar air emits light of its own accord — no support

Why: Nothing it remembers matched the question, so it guessed: it took the first option shown. · the question and its options parsed, with trees and pragmatics

This page in Markdown → https://md.mova.elamur.ai/free/en/school-run/physics/30-compasses-and-the-magnetic-earth/