# Electro magnet repulsion

1. Jan 12, 2014

### johntee

1. The problem statement, all variables and given/known data

My 10 year old granddaughter started her new school term last week and was presented with an electromagnet problem by her new science teacher. The class is allowed to use any non-physical method to solve this for their lesson next Wednesday. A direct link to my 'Dropbox' account show the picture she was given at school.

She needs to know:- Will the example electro-magnets repelling force of one kilogram be applied equally to each of the permanent magnets, or will the repelling force be divided by two, equating to the one kilogram electro-magnet force exerting 0.5 kilogram against each of the permanent magnets?

2. Relevant equations

https://www.dropbox.com/s/srdn5w8krhlpgth/Electro-magnet%20-%20Copy.jpg

3. The attempt at a solution

Only me of course; Granddad can sort anything out :!!) Oh the faith of children.

Thanks in advance,

John

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Jan 12, 2014

### tiny-tim

hello johntee! welcome to pf!

ask your granddaughter what she would expect to happen if the electromagnet were glued to the floor

3. Jan 12, 2014

### johntee

Hi tiny-tim,

Thanks for your welcome. Apparently the electromagnetic is glued to the floor and the permanent magnets can only move outwards in the directions as shown by the arrows, I did not realize that when posting her question. She recognizes the permanent magnets could spin around and stick to the electromagnet, but that is not what her teacher requires, he wishes the class to evaluate the repelling push pressure if an individual pressure gauge was placed on each outside end of the fixed magnets. Will the gauges each show one kilogram or would they show 0.5 kilograms. I hope this makes sense to you, I 'fluffed' at physics during my school days in the 1950's so I don't have a clue how to explain things better.

Thanks,

John

PS. My daughter will be carting my granddaughter off to her bath and thereafter bed shortly in readiness for school at 6:30 am in the morning. I dare not ring after about 7:00pm. My daughter is a school teacher so double school runs start early.

Last edited: Jan 12, 2014
4. Jan 12, 2014

### tiny-tim

hi john!
ah, so if there was only one permanent magnet, its gauge would show 1 kg

does your granddaughter know anything about forces? or tension or compression?

would it make any sense to ask your granddaughter what force the glue exerts on the electromagnet?

5. Jan 12, 2014

### johntee

Hello again tiny-tim,

Just got off the phone to her, my daughter had to break her away from her iPad. I explained that if there was one magnet in place the permanent magnet gauge would show 1 Kg, whereupon she asked what about the other gauge on the other magnet. Of course I could not answer. The class only started science lessons last September and are only on fundamentals, i.e. Basic circuits using LED's and batteries to demonstrate such. They were intruded to permanent magnets before Christmas. She doesn't know anything about the forces / tensions / compressions, I assume they would come later in her science schooling. All the class was told was the electromagnet is fixed to the floor and the permanent magnets were being repelled, no mention of glues etc. I personally believe their teacher is looking for a basic result of the supplied photograph, a test of their intuition maybe rather than a result inclusive of any untaught laws at the moment?

Once again, I cannot assist her further hence my posting here.

Thanks,

John

PS. My daughter will be carting my granddaughter off to her bath and thereafter bed shortly in readiness for school at 6:30 am in the morning. I dare not ring after about 7:00pm. My daughter is a school teacher so double school runs start early.

Last edited: Jan 12, 2014
6. Jan 12, 2014

### tiny-tim

hi john!
i don't think we can give her any more help

from here, she'll have to apply her female intuition!
erm

i'd need to know your time-zone!

7. Jan 12, 2014

### johntee

Electro magnetic repulsion

Hi tiny-tim,

I thought a forum like this would be the most promising avenue to solving my granddaughter's school problem in a very basic way, unfortunately not, unless any other members can assist us.

I have contacted an old school chum who made his living in the electronics field and he is going to get one of his staff to make a physical demonstration model of the fixed electromagnet and permanent magnets in the picture configuration as sent home from school. Whilst my granddaughter is forbidden to use such to solve her homework, she intends to take it into her school science class next Wednesday for her teachers evaluation. Maybe it will become a science class feature for other young pupils to use in the future.

In fairness, I don't think a child of ten years has developed the ability to apply 'female' intuition' to such a scientific challenge yet, with four months into the art being hardly suffice. So to the rescue comes 'good old, and wise granddad' once again. Children so obviously need our help in their early development years and it's to we, the adults, who need to rally to their assistance in any way we can.

Our time zone is that of the United Kingdom at present.

John

8. Jan 12, 2014

### tiny-tim

ah, this forum does not solve people's problems,

it only helps them to solve them themselves

9. Jan 12, 2014

### johntee

Hi tiny-tim,

I would have welcomed that information after my first post when I requested such. It could have saved me valuable time pursuing a negative.

John

10. Jan 12, 2014

### tiny-tim

I assumed that you had read the forum's Rules and Guidelines.

11. Jan 12, 2014

### johntee

Hi tiny-tim,

Obviously not, a throw back from me being a professional architect ( now retired ). I delegated others to do that on my behalf whilst I got on with my main role in structural engineering and desgn.

John

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