O'levels Physics questions
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Hey all :D Here's some questions that I feel isn't clearly explained in the textbook and so I need your help in a more elaborate and comprehensible way to explain these questions to me, thank you so so so much!
- DC Motor. We all know to increase the turning effect, we have to
1) Increase the current supplied.
2) Insert a soft iron core within the coil.
3) Increase the number of turns of the coil.
4) Use a pair of stronger magnets.
But the thing is, I don't fully understand the theory behind all these. Anyone care to explain?
- AC Generator. The purpose of the slip rings as it states in the textbook is so that "the alterating induced current in the coil is transferred to the external circuit". So does that mean that without the slip rings, the induced e.m.f is lost to the surroundings or does it keep 'flowing' throughout the coil? And according to a longman assessment, they stated that the purpose of the slip rings is so as to prevent the coil from entanglement. So what exactly is the correct explanation?
- Charges. For example, if a positively charged conductor is allowed to come near the left of an neutral object, the electrons in the object will be attracted to the left and the protrons will be repelled away to the right side. Thus, there will be attraction between the conductor and the object but once they touch instantaneously, some of the electrons were transferred to the positive conductor thus causing the object to become positively charged (since it lost some electrons) and repel away from the positive conductor, right? Then why is it for example in crop-spraying it states that the positively charged droplets induces negative charges on the plants as they come closer to the plants, allowing attraction. So, when do I know it's induction or something? And when the droplets reach the plants, does that mean that the plants become negatively charged or positively charged?
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I'll have to TRY to answer the others later. I am a Secondary Four student (Triple-Science, Elect Geog) too, so pardon me if i make any mistakes.
- AC Generator. The purpose of the slip rings as it states in the textbook is so that "the alterating induced current in the coil is transferred to the external circuit". So does that mean that without the slip rings, the induced e.m.f is lost to the surroundings or does it keep 'flowing' throughout the coil? And according to a longman assessment, they stated that the purpose of the slip rings is so as to prevent the coil from entanglement. So what exactly is the correct explanation?
Slip rings ensure that the direction of the induced e.m.f./current flowing in the EXTERNAL circuit changes every half revolution (that is, every 180 degrees turn) to produce an ALTERNATING CURRENT (main purpose of A.C. GENERATOR)
The purpose of the slip rings as it states in the textbook is so that "the alterating induced current in the coil is transferred to the external circuit". So does that mean that without the slip rings, the induced e.m.f is lost to the surroundings or does it keep 'flowing' throughout the coil? I don't know about this. This is very vague and debatable (induced current flows in the cables).
The Longman Book is not wrong to say prevention of coil entanglement, because without the slip rings, try to visualise if you were to turn the coil. How would the connecting cables in the EXTERNAL circuit be affected? Or rather, how would the external circuit, on a whole, be affected?
- Charges. For example, if a positively charged conductor is allowed to come near the left of an neutral object, the electrons in the object will be attracted to the left and the protrons will be repelled away to the right side. Thus, there will be attraction between the conductor and the object but once they touch instantaneously, some of the electrons were transferred to the positive conductor thus causing the object to become positively charged (since it lost some electrons) and repel away from the positive conductor, right? Then why is it for example in crop-spraying it states that the positively charged droplets induces negative charges on the plants as they come closer to the plants, allowing attraction. So, when do I know it's induction or something? And when the droplets reach the plants, does that mean that the plants become negatively charged or positively charged?
the electrons in the object will be attracted to the left and the protrons will be repelled away to the right side. The protons don't move. It is very easy for them to find fault with you if you say that the protons are repelled to the right (although it is not wrong to say so). Just state that electrons are attracted to the left and the protons are LEFT at the right, INDUCING the right side with a positive charge (and vice-versa).
to become positively charged. To be INDUCED with a positive charge (though I can't find any difference, but my teacher emphasised on using this)
Then why is it for example in crop-spraying it states that the positively charged droplets induces negative charges on the plants as they come closer to the plants, allowing attraction. So, when do I know it's induction or something? And when the droplets reach the plants, does that mean that the plants become negatively charged or positively charged? What textbook does your school use? Mind uses the Pearson Longman Physics Insights, 2nd Edition (no sorry, I don't have a scanner). Mine gives an example on Electrostatic Paint Spraying. I think you just have to understand that induction precedes attraction. Induce negative charges on plant --> attraction --> charges between droplets and plant are neutralised (since they come into contact) --> electrically neutral plant.
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Hey! Thanks so much, I think you've been a great help, really! :) My textbook is the Marshall Cavendish Education GCE 'O' Level Physics Matters (which isn't very good in my opinion ><).
So it means in static electricity, I ALWAYS use the word 'induce' a charge on and adds on that the electrons are attracted and not the protons are repelled? Similarly for paint spraying and crop-spraying, both also inducing charge right? =)
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wow
not going back to sch to clear things up?????
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Heyo! I have enough questions on questions to bombard my teacher with already, hahaha. And she has specific consultation hours, and I'm not the only one seeking help, so I guess I'll clear such concepts here. Hahaha.
And btw Garrick, I'm a triple science, literature elective student. xD
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i think u btr ask ur teacher double confirm
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It is very thoughtful of you, to consider your teacher's workload. Man, I feel guilty that I just made an appointment with my Chemistry Teacher tmr :(
I think induce is a better word. After all, this is INDUCTION under static electricity.
I'll have to think about your DC motor question later.
EDIT: Yeah, ask teacher, or ask the top students in your class/school.
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Hahaha, alright thanks for your help! I guess I'll try to clear my doubts and then reply back here for anyone to reference later on too. (:
And yes y_shun, you help me double confirm la, HAHA.
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Originally posted by Garrick_3658:
It is very thoughtful of you, to consider your teacher's workload. Man, I feel guilty that I just made an appointment with my Chemistry Teacher tmr :(
I think induce is a better word. After all, this is INDUCTION under static electricity.
I'll have to think about your DC motor question later.
EDIT: Yeah, ask teacher, or ask the top students in your class/school.
No need to feel guilty.
If you ask questions, it makes your teacher feel even better when they know you cleared up your doubts, instead of staying quiet.
I don't want to dig out my notes >.<! -
Originally posted by Garrick_3658:
I'll have to TRY to answer the others later. I am a Secondary Four student (Triple-Science, Elect Geog) too, so pardon me if i make any mistakes.
- AC Generator. The purpose of the slip rings as it states in the textbook is so that "the alterating induced current in the coil is transferred to the external circuit". So does that mean that without the slip rings, the induced e.m.f is lost to the surroundings or does it keep 'flowing' throughout the coil? And according to a longman assessment, they stated that the purpose of the slip rings is so as to prevent the coil from entanglement. So what exactly is the correct explanation?
Slip rings ensure that the direction of the induced e.m.f./current flowing in the EXTERNAL circuit changes every half revolution (that is, every 180 degrees turn) to produce an ALTERNATING CURRENT (main purpose of A.C. GENERATOR)
The purpose of the slip rings as it states in the textbook is so that "the alterating induced current in the coil is transferred to the external circuit". So does that mean that without the slip rings, the induced e.m.f is lost to the surroundings or does it keep 'flowing' throughout the coil? I don't know about this. This is very vague and debatable (induced current flows in the cables).
The Longman Book is not wrong to say prevention of coil entanglement, because without the slip rings, try to visualise if you were to turn the coil. How would the connecting cables in the EXTERNAL circuit be affected? Or rather, how would the external circuit, on a whole, be affected?
- Charges. For example, if a positively charged conductor is allowed to come near the left of an neutral object, the electrons in the object will be attracted to the left and the protrons will be repelled away to the right side. Thus, there will be attraction between the conductor and the object but once they touch instantaneously, some of the electrons were transferred to the positive conductor thus causing the object to become positively charged (since it lost some electrons) and repel away from the positive conductor, right? Then why is it for example in crop-spraying it states that the positively charged droplets induces negative charges on the plants as they come closer to the plants, allowing attraction. So, when do I know it's induction or something? And when the droplets reach the plants, does that mean that the plants become negatively charged or positively charged?
the electrons in the object will be attracted to the left and the protrons will be repelled away to the right side. The protons don't move. It is very easy for them to find fault with you if you say that the protons are repelled to the right (although it is not wrong to say so). Just state that electrons are attracted to the left and the protons are LEFT at the right, INDUCING the right side with a positive charge (and vice-versa).
to become positively charged. To be INDUCED with a positive charge (though I can't find any difference, but my teacher emphasised on using this)
Then why is it for example in crop-spraying it states that the positively charged droplets induces negative charges on the plants as they come closer to the plants, allowing attraction. So, when do I know it's induction or something? And when the droplets reach the plants, does that mean that the plants become negatively charged or positively charged? What textbook does your school use? Mind uses the Pearson Longman Physics Insights, 2nd Edition (no sorry, I don't have a scanner). Mine gives an example on Electrostatic Paint Spraying. I think you just have to understand that induction precedes attraction. Induce negative charges on plant --> attraction --> charges between droplets and plant are neutralised (since they come into contact) --> electrically neutral plant.
Very very well done. You are well on your way to an A1 :D
I shall add on a bit
The purpose of the slip rings as it states in the textbook is so that "the alterating induced current in the coil is transferred to the external circuit". So does that mean that without the slip rings, the induced e.m.f is lost to the surroundings or does it keep 'flowing' throughout the coil? I don't know about this. This is very vague and debatable (induced current flows in the cables).
Without slip rings, or rather, without a complete circuit, there will be no induced current. Rather, there will be an induced voltage.
The reason is because of the force on the moving electrons. When wires move in a magnetic view, you can visualise lots of electrons moving in the wire moving in the field as well... Something like that... There will be a force on the electrons to move to one side, and hence creating a potential difference. If it is a complete circuit, these electrons will continue to move in the circuit, resulting in the induced current :D
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Hey eagle, thanks for your add on :D I get the part on induction and AC generator already! =) But I'm still curious about this:
- DC Motor. We all know to increase the turning effect, we have to
1) Increase the current supplied.
2) Insert a soft iron core within the coil.
3) Increase the number of turns of the coil.
4) Use a pair of stronger magnets.For number 2), I understand that it is to concentrate the magnetic field lines, but I don't really know how to put it across properly, like, do I say it is because when the lines are concentrated that the "field is stronger" or do I mention about how "more lines are linked to the conductor"? =/ Both sounds wrong T.T
As for 1,3 and 4, I have seriously no idea. -
Originally posted by iamapebble:
Hey eagle, thanks for your add on :D I get the part on induction and AC generator already! =) But I'm still curious about this:
- DC Motor. We all know to increase the turning effect, we have to
1) Increase the current supplied.
2) Insert a soft iron core within the coil.
3) Increase the number of turns of the coil.
4) Use a pair of stronger magnets.For number 2), I understand that it is to concentrate the magnetic field lines, but I don't really know how to put it across properly, like, do I say it is because when the lines are concentrated that the "field is stronger" or do I mention about how "more lines are linked to the conductor"? =/ Both sounds wrong T.T
As for 1,3 and 4, I have seriously no idea.Something like this, correct me if i'm wrong.
Magnetic field + current = motion
Increases magnetic field + current = Increased motion
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Originally posted by iamapebble:
Hey eagle, thanks for your add on :D I get the part on induction and AC generator already! =) But I'm still curious about this:
- DC Motor. We all know to increase the turning effect, we have to
1) Increase the current supplied.
2) Insert a soft iron core within the coil.
3) Increase the number of turns of the coil.
4) Use a pair of stronger magnets.For number 2), I understand that it is to concentrate the magnetic field lines, but I don't really know how to put it across properly, like, do I say it is because when the lines are concentrated that the "field is stronger" or do I mention about how "more lines are linked to the conductor"? =/ Both sounds wrong T.T
As for 1,3 and 4, I have seriously no idea.Hi
The induced force is directly proportional to the magnetic field and current (paiseh, I forgot the exact formula at the moment).
Visualise one more thing. When there's current in a coil, there's a circular magnetic field. This magnetic field interacts with the magnetic field of the magnets and results in a force. Thus, the stronger these two magnetic fields are, the larger the repelling, or attractive, force.
In short, all of the above actually serves to increase the magnetic fields one way or the other....
Anyway for O levels, I'm not sure if you need to really explain the above...
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Originally posted by eagle:
Hi
The induced force is directly proportional to the magnetic field and current (paiseh, I forgot the exact formula at the moment).
Visualise one more thing. When there's current in a coil, there's a circular magnetic field. This magnetic field interacts with the magnetic field of the magnets and results in a force. Thus, the stronger these two magnetic fields are, the larger the repelling, or attractive, force.
In short, all of the above actually serves to increase the magnetic fields one way or the other....
Anyway for O levels, I'm not sure if you need to really explain the above...
There isn't any formula if i remembered correcting for O-levels.
I don't think have to explain so much as most likely only 2 points.
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Originally posted by eagle:
Hi
The induced force is directly proportional to the magnetic field and current (paiseh, I forgot the exact formula at the moment).
Visualise one more thing. When there's current in a coil, there's a circular magnetic field. This magnetic field interacts with the magnetic field of the magnets and results in a force. Thus, the stronger these two magnetic fields are, the larger the repelling, or attractive, force.
In short, all of the above actually serves to increase the magnetic fields one way or the other....
Anyway for O levels, I'm not sure if you need to really explain the above...
Hey, thanks for your reply. :D I didn't know about "The induced force is directly proportional to the magnetic field and current." I guess I haven't learn it? Haha, anyway I was just curious because it's a question in a NGS prelim paper whereby they asked why the turning effect will increase when the number of turns of coil increase and when a stronger magnet is used.
I guess it's not required as of now, but just wondering. :D Thanks so much!P/S: thanks crimsontactics too! (: