Q&A - PSLE Science

[atutor2001]

Belle2011:

May I find out if magnetism can pass through magnetic materials? Can you give an example to show it?

I guess you must have read somewhere that magnetism pass through ALL materials (including magnetic material), which is actually correct.

The problem lies with the definition of \"pass through\".

In primary school, \"pass through\" is defined as going in from one side and coming out directly from the opposite side, using the shortest path.

In scientific definition, \"pass through\" means going into the magnetic material, using whatever path that the magnetic force would like to travel inside the magnetic material, and then coming out of the magnetic material. Therefore, the more accurate definition is

\"Magnetic material will redirect magnet force.\"

If a steel sheet is placed in front of a magnet, magnetic force prefers to travel through the steel sheet than through air. As a result, it will take the longest path available inside the steel sheet and comes out of the sheet at the edges. As a result, any object placed directly on the opposite side of the steel sheet will not experience any magnetic force as the force would not come out through the \"broad surface\" but through the edges.

[Belle2011]

atutor2001:

I guess you must have read somewhere that magnetism pass through ALL materials (including magnetic material), which is actually correct.

This is the tricky part; in school nothing much was mentioned and we have a feeling that magnetism can't pass through magnetic materials.
But when you put a magnet near an iron nail, this iron nail can in turn attracts some iron filings or paper clips which means the magnetism has passed from the magnet to the iron nail.
I am getting more and more confused.
Cheers,
Belle.

[tianzhu]

Belle2011:

May I find out if magnetism can pass through magnetic materials?

Belle2011:

This is the tricky part; in school nothing much was mentioned and we have a feeling that magnetism can't pass through magnetic materials.
But when you put a magnet near an iron nail, this iron nail can in turn attracts some iron filings or paper clips which means the magnetism has passed from the magnet to the iron nail.
I am getting more and more confused.

Hi

In PSLE science, students learned that magnetic force cannot pass through magnetic materials.

What you’ve described is an example of magnetism by induction. The iron nail is magnetised by induction.

Best wishes

[atutor2001]

tianzhu:

What you’ve described is an example of magnetism by induction. The iron nail is magnetised by induction.

Best wishes

Magnetic induction is the result of magnetic force passing through the iron nail (a magnetic material). I have copied this write-up from the internet :

\"As an iron nail is brought close to a bar magnet, some flux lines emanating from the north pole of the magnet pass through the iron nail in completing their magnetic path. Since magnetic lines of force travel inside a magnet from the south pole to the north pole, the nail will be magnetized in such a polarity that its south pole will be adjacent to the north pole of the bar magnet. There is now an attraction between the two magnets.\"

For those interested, you may visit this site
http://www.tpub.com/neets/book1/chapter1/1i.htm

In my opinion, it is important to teach our kids the truth and also to accept the limitation of the primary science syllabus - recognising the difference in definitions of the words used.

[tianzhu]

Hi Belle2011


You may wish to try out these questions. I think it’ll help.

Do a recap of what you’ve been in lower primary science.
Magnetism refers to the pull of a magnet, the magnetic force of attraction and repulsion.

Q3 and Q4 of this link.
http://www.oldschool.com.sg/index.php/module/PublicAccess/action/Wrapper/sid/597167a402eb2fb7800f02ccf96c7860?srch_str=&sub_cat_nm=Magnets&qn_type=QN&cat_grp_id=69&srch_press.x=43&srch_press.y=12

Q10 of this link.
http://www.oldschool.com.sg/index.php/module/PublicAccess/action/Wrapper/sid/597167a402eb2fb7800f02ccf96c7860?srch_str=&sub_cat_nm=Magnets&qn_type=QN&cat_grp_id=85&srch_press.x=36&srch_press.y=9

Best wishes

[ParentingChildren]

Don’t think the concept of magnetic shielding is in the Primary Science Syllabus.

[Nebbermind]

ParentingChildren:

Don't think the concept of magnetic shielding is in the Primary Science Syllabus.

obviously not. but there are enough diagrams to to illustrate how the magnetic fields are altered when a magnetic material is placed near the magnet. Even if the diagrams are not helpful, the term 'magnetic shielding' is kinda self explanatory

[meimeitan]

Hi Good morning,


Anyone can help the following question?

Tubes grow from the pollen grains towards the ovary to pass __________
(1) the pollen grains to the ovules
(2) nutrients and water to the ovules
(3) the female egg cells to the ovules
(4) the male reproductive cells to the ovules

Thanks.

[starlight1968sg]

meimeitan:

Hi Good morning,


Anyone can help the following question?

Tubes grow from the pollen grains towards the ovary to pass __________
(1) the pollen grains to the ovules
(2) nutrients and water to the ovules
(3) the female egg cells to the ovules
(4) the male reproductive cells to the ovules

Thanks.

I think is (1). Let us hear what the other say.

[Nebbermind]

IIRC, shd be (4)