Hi,
For Q1, please read:
http://www.electronics-tutorials.ws/electromagnetism/electromagnets.html
For Q2, please read the bottom of:
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/elemag.html
Thanks.
Cheers,
Wen Shih
1) Each coil produces a force. More coils produce more force. They vector summed
2) Magnetic force intensity and closeness of field lines are related. The closer the field lines are together, the stronger the force.
How (2) looks like should be in your textbook, else it will not be in your syllabus. I cannot remember if closeness of field lines are in your syllabus.
Originally posted by StudentQns:Hi I have another physics question to ask. For example when a steel is placed in between a solenoid and a current is turned on, it attracts 10 iron tacks. When I turn it off will it have like 10 still or less? I know that steel is a hard magnetic material which retains its magnetism for a long time. So in theory do I consider it to retain all of its magnetism? Thanks for all the help!
For O levels, consider steel to retain all its magnetism. I believe you will only be tested on whether it retains its magnetism well, of which the answer is yes.
Originally posted by StudentQns:Here’s what I think:
When they just say a ‘current’ flows through the solenoid. then this means that the magnet induced is not strong enough to completely over right the earth’s magnetic. so when I turn off the current it will deviate slightly back into its original position.if they say ‘large current’ it will totally over right the earth magnetic field. and when I remove it it still retains a while bunch of magnetism so it doesn’t deviate at all.
this is something like what my teacher said. but I’m not sure as even hard magnetic material loses some of its magnetism once current is turned off. just that it retains it longer as compared to iron
thanks for all the help
Is your first paragraph referring to the behaviour of a compass situated just outside the solenoid?
Originally posted by eagle:Is your first paragraph referring to the behaviour of a compass situated just outside the solenoid?
Was too busy with work
I saw your questions in physicsforum.com too. I hope you realise that by posting part of a question, or paraphrasing it in your own words, you could potentially be changing the whole question into an entirely different one, confusing yourself even more in the process. You could also be imposing impossible limtations or scenarios that cannot be solved, things that teachers would have considered before setting the question. And that is not the way to ask for help online.
Also, when seeking for help online, you need to let others know which level you are at so that help can be pitched at the right level. Whatever is being taught at O level physics is so grossly insufficient and inadequate that a number of concepts are overly simplified and have severe limitations when we go on to higher level physics. i.e. Newton's 2nd law is force times acceleration in O levels, but it has a different definition at A levels, and an even more complicated usage in Uni.
Please see our Guidelines for homework forum
Please post the exact wording of the question, as well as what you have attempted or found out.
Thanks.
Concept is totally wrong
Force and energy cannot be linked like this. One is a vector, and one is a scalar. They are totally different.
"So a 100J energy might have more force than a 200J energy because of this changed variable-distance." -- this is totally wrong!
Energy is the ability to do work. You cannot say 100J has more force --> This is horrendously wrong!
You can only say that 100J of energy has lesser ability to do work as compared to 200J of energy.
Force is a vector. A force can do work.
When a force does work, you get work done. However, a force can do zero work as well.
Apart from that, there's actually not much linkage... Do try not to link these two.