HELP! GCSE Physics... (Electromagnetic induction) Watch

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icy_shadow2006
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hi, i am to take my triple science Physics GCSE exam and i am really confused with electro-magnets.

What is EM induction, text books on the on this confuse me, what is Flux cutting and why do u need a split ring commutator in motors???

Any help would be nice!
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icy_shadow2006
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help plz
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(Original post by icy_shadow2006)
hi, i am to take my triple science Physics GCSE exam and i am really confused with electro-magnets.

What is EM induction, text books on the on this confuse me, what is Flux cutting and why do u need a split ring commutator in motors???

Any help would be nice!
Ok mate... lets see

Em induction is electromagnetic induction. So this is the eneration of a current in a wire when it is moved through a magnetic field. This is how dynamos work.

A magnet produces field lines ok... so when you move a wire through these then you displace electrons in the wire and generate a current. Thats basically all there is. The key thing to realise is that the wire must be moving. This is the flux cutting business. So flux cutting is the number of field lines of magnetic field that are cut. The more that are cut by the wire the stronger the current. By cut I mean the number of field lines that pass through the wire. So we can have more flux cut if we have a stronger field, so there are more field lines, or if we move the wire faster, as then we shall cut more lines in the same time. So thats flux cutting.

Split ring commutator is there to allow the wire to turn. If we have a loop in of wire in a magnetic field it will turn. This si the principle of the electric motor. This is induction in reverse. We put a current through the wire and so create a force from the magnetic field that turns the wire. Now if we didnt have a commutator the wire would just twist & tangle up. So it stops that happening. Also after each half cylce it is necessary to reverse the current direction so as to maintain the force. Otherwise it would do half a turn & just stop. Therefore the commutator just allows the motor to function properly.

I hope you understood all that and it helps, if not ask and me or someone else can try again
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icy_shadow2006
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thanx a bunch, i understand it now!!
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smurfride
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i remember this one;
basically when a conductor crosses lines of a magnetic field it produces an electromotive force in the wire and can produce a current in it. it must cut the lines of the magnetic field/ magnetic flux and not go alongside them, it has to be at right angles. -the size of the current increases if you move the conductor accrose these lines more quickly or increase the strength of the magnet. just think- electromagnetic induction-you induce a current by putting a condutor of electricity accross a magnetic field.

onto motors- the motor effect is producing motion by passing a wire already carrying a current, accross magnetic field lines. i always think 'motor' as in inducing motion of the wire. in motors you need a split ring commutator because -if you have a picture of one there i'll expain or draw it as i explain-
you have a c shaped magnet with north on the left and south on the right, with a coil in the middle attatched to a power supply with the positive on the right. this means the left side of the coil eperiences a force -an electromotive force. so begins o move. to the right . howvere when it reaches a vertical position it is cuttin no lines of flux( field lines) but because of its inertia which is its resistance to change its motion it overshoots the vertical and the commutators switch sides reversing the current. this should be all you know for gcse and don';t worry too much hope that helps!!!
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smurfride
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think i was a bit late then!! lol
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