Why can a horseshoe magnet not magnetise a steel spoon?

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Why can a horseshoe magnet not magnetise a steel spoon?

Postby atrecord » Sun Oct 21, 2012 1:18 pm

One more P3 science question that baffled me, but more importantly, also ex-teacher-friend who taught 'O' level Physics before...

There is a question in DD's science practice paper, that first asked about having a bar magnet magnetise a steel spoon by stroking in one direction for 30 times, which is fine.

Then the second part asked the student to give one possible reason why would a horseshoe magnet not be able to magnetise a similar steel spoon.

It is a 'fill in the blank' (or for higher level, called a structured question) type of question (not a MCQ), has 3 lines for the answer -- and is only for 1 mark!

Anyone can advise what is the correct answer?

tks...

atrecord
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Re: Why can a horseshoe magnet not magnetise a steel spoon?

Postby linden2000 » Sun Oct 21, 2012 3:05 pm

atrecord wrote:One more P3 science question that baffled me, but more importantly, also ex-teacher-friend who taught 'O' level Physics before...

There is a question in DD's science practice paper, that first asked about having a bar magnet magnetise a steel spoon by stroking in one direction for 30 times, which is fine.

Then the second part asked the student to give one possible reason why would a horseshoe magnet not be able to magnetise a similar steel spoon.

It is a 'fill in the blank' (or for higher level, called a structured question) type of question (not a MCQ), has 3 lines for the answer -- and is only for 1 mark!

Anyone can advise what is the correct answer?

tks...


Let me try:

When stroking with a bar magnet, one distinct pole of the bar magnet comes into contact with the steel spoon. However for a horseshoe magnet due to its curved shape, its poles are very close to each other and both poles of the horseshoe magnet may come into contact with the steel spoon during the stroking. Hence, no distinct poles are created and the spoon will not be magnetised.

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Re: Why can a horseshoe magnet not magnetise a steel spoon?

Postby verykiasumummy » Sun Oct 21, 2012 3:56 pm

linden2000 wrote:
atrecord wrote:One more P3 science question that baffled me, but more importantly, also ex-teacher-friend who taught 'O' level Physics before...

There is a question in DD's science practice paper, that first asked about having a bar magnet magnetise a steel spoon by stroking in one direction for 30 times, which is fine.

Then the second part asked the student to give one possible reason why would a horseshoe magnet not be able to magnetise a similar steel spoon.

It is a 'fill in the blank' (or for higher level, called a structured question) type of question (not a MCQ), has 3 lines for the answer -- and is only for 1 mark!

Anyone can advise what is the correct answer?

tks...


Let me try:

When stroking with a bar magnet, one distinct pole of the bar magnet comes into contact with the steel spoon. However for a horseshoe magnet due to its curved shape, its poles are very close to each other and both poles of the horseshoe magnet may come into contact with the steel spoon during the stroking. Hence, no distinct poles are created and the spoon will not be magnetised.


agree... the poles of horseshoe magnet are too close to each other, hence couldnt magnetise the spoon

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Re: Why can a horseshoe magnet not magnetise a steel spoon?

Postby atrecord » Sun Oct 21, 2012 10:50 pm

Thanks... sounds like a plausible answer.
But what if i were to change it to a U-shaped magnet then?

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Re: Why can a horseshoe magnet not magnetise a steel spoon?

Postby ammonite » Wed Oct 24, 2012 11:45 pm

I will have a go. The magnet has been dropped many times or heated and thus has lost much of its magnetising power.

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Re: Why can a horseshoe magnet not magnetise a steel spoon?

Postby funlearner » Mon Oct 29, 2012 9:54 pm

The way which the horseshoe magnet is used to stroke the steel spoon is not mentioned. If the poles are used to stroke the magnet, the steel spoon must have retained some magnetic strength (no matter how close the N-pole and S-pole are together). I think one possible way for it to happen is to use the curve part (where N-pole and S-pole physically meet) of the horseshoe magnet to stroke the steel spoon.

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