به انگلیسی

Magnetic Fields

علوم · نیروها و حرکت · ages 11-12

Name ______________________ Date ____________

Ana wants to record field direction at different places around a bar magnet. Which tool should she move from place to place?
- A compass with a freely turning needle
- A ruler with centimetres marked on it
- A spring with a scale for measuring force
The lines on a magnetic field map are real threads floating around the magnet.
Circle one: True False
Mia brings a bar magnet near a compass. Why can the needle turn to line up with the field?
- It is a needle turned by warmth from Mia's hand
- It is a small magnet mounted so it can turn
- It is a needle turned north by gravity alone
Away from magnetic objects, a compass helps Lina face north. Her route says to travel east. Which way should she turn?
- A quarter-turn to her left
- A half-turn to face behind
- A quarter-turn to her right
Ravi records field direction at 3 places near the north pole, 3 near the south pole and 4 along the sides. Each place is different. How many readings does he record?
Answer: ______________
Ravi's field sensor reads 10 units at one position and 4 units at another. How many units did the reading drop?
Answer: ______________
A sailor's compass changes direction beside a speaker. Farther away, its reading becomes steady. What should the sailor do before choosing a route?
- Use the reading beside the speaker without checking it
- Move away from the speaker and read the compass again
- Press the compass against the speaker and use that reading
Mia's sensor reads 8 units. After she changes the setup, the measured reading doubles. What is the new reading?
Answer: ______________
Omar imagines Earth's magnetic field and all other magnetic fields vanishing. Would a compass still have a magnetic reason to point north?
- No; no magnetic field would guide its direction
- Yes; gravity would guide its north tip northward
- Yes; sunlight would guide its north tip northward
Zara brings a bar magnet near a compass. Its field at the needle is much stronger than Earth's field and points a different way. What happens?
- The needle keeps pointing north despite the stronger nearby field
- The needle turns to nearly follow the bar magnet's field
- The needle loses both magnetic poles and stops responding to fields

Answer key

For grown-ups. Fold this page away before handing over the rest.

Magnetic Fields W1-mt_56aspHjU19-s1

A compass with a freely turning needle · A compass's north tip shows field direction. A ruler measures length; a force spring does not supply a compass direction reading.
False · Field lines are a drawing tool for representing a magnetic field. They are not physical threads.
It is a small magnet mounted so it can turn · The needle is a small magnet that can turn. A magnetic field can turn it into alignment.
A quarter-turn to her right · Facing north, east is on the right. Lina should make a quarter-turn to her right.
10 · Count every different place once: 3 plus 3 plus 4 equals 10 readings.
6 · Subtract the final reading from the first: 10 minus 4 equals 6 units.
Move away from the speaker and read the compass again · A speaker's magnet can disturb a compass. The sailor should take a settled reading away from it before choosing a route.
16 · The question states that the reading doubles. Two times 8 equals 16 units.
No; no magnetic field would guide its direction · With no magnetic field present, the needle has no magnetic reason to choose north.
The needle turns to nearly follow the bar magnet's field · The needle follows the combined field. Since the magnet's field is much stronger, that direction is close to the magnet's field direction.