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Why does Electric Field Strength [Vector] point in the direction of a positive charge
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Mihael_Keehl
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#1
okey
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Absent Agent
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#3
(Original post by Mihael_Keehl)
mmmn
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Mihael_Keehl
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#4
(Original post by Mehrdad jafari)
I guess that would be the case if it was the positive charge was creating the electric field.
I guess that would be the case if it was the positive charge was creating the electric field.
Maybe I overcomplicated it..
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Absent Agent
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#5
(Original post by Mihael_Keehl)
EFS = Force experienced per unit positive charge so I suppose it is using a positive test charge to analyse what direction the force is travelling in?
Maybe I overcomplicated it..
EFS = Force experienced per unit positive charge so I suppose it is using a positive test charge to analyse what direction the force is travelling in?
Maybe I overcomplicated it..
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Mihael_Keehl
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#6
(Original post by Mehrdad jafari)
If the negative charge is causing the field, the direction of the force will be towards the negative charge as the positive test charge will be attracted towards the positive charge.
If the negative charge is causing the field, the direction of the force will be towards the negative charge as the positive test charge will be attracted towards the positive charge.
I understand the latter part: but with EFS isn't it always the positive charge that is causing the field?
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EricPiphany
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Absent Agent
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#8
(Original post by Mihael_Keehl)
I understand the latter part: but with EFS isn't it always the positive charge that is causing the field?
I understand the latter part: but with EFS isn't it always the positive charge that is causing the field?
, where one of the charges is negative, mathematically gives the negative sign for the force direction, even if the negative charge is the test charge.
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Mihael_Keehl
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#9
(Original post by Mehrdad jafari)
Yes, it could be, but the direction of the field lines will be away from the positive charge causing the field and towards the positive test charge, i.e the force will be towards the positive test charge (and not towards the positive charge causing the field). Fundamentally, the direction of the field lines has been defined to be always directed towards the negative charge, because Coulomb's equation , where one of the charges is negative, mathematically gives the negative sign for the force direction, even if the negative charge is the test charge.
Yes, it could be, but the direction of the field lines will be away from the positive charge causing the field and towards the positive test charge, i.e the force will be towards the positive test charge (and not towards the positive charge causing the field). Fundamentally, the direction of the field lines has been defined to be always directed towards the negative charge, because Coulomb's equation
, where one of the charges is negative, mathematically gives the negative sign for the force direction, even if the negative charge is the test charge.
Thank You.
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alow
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Absent Agent
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Mihael_Keehl
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#12
(Original post by Mehrdad jafari)
Yes, it could be, but the direction of the field lines will be away from the positive charge causing the field and towards the positive test charge, i.e the force will be towards the positive test charge (and not towards the positive charge causing the field). Fundamentally, the direction of the field lines has been defined to be always directed towards the negative charge, because Coulomb's equation , where one of the charges is negative, mathematically gives the negative sign for the force direction, even if the negative charge is the test charge.
Yes, it could be, but the direction of the field lines will be away from the positive charge causing the field and towards the positive test charge, i.e the force will be towards the positive test charge (and not towards the positive charge causing the field). Fundamentally, the direction of the field lines has been defined to be always directed towards the negative charge, because Coulomb's equation
, where one of the charges is negative, mathematically gives the negative sign for the force direction, even if the negative charge is the test charge.
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Absent Agent
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#13
(Original post by Mihael_Keehl)
I must finally ask, from my reading I have assumed that the test charge taken to help us determine the direction of the field lines is positive, so is this assumption wrong since your last statement say we can take the test charge to be negative?
I must finally ask, from my reading I have assumed that the test charge taken to help us determine the direction of the field lines is positive, so is this assumption wrong since your last statement say we can take the test charge to be negative?
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Mihael_Keehl
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#14
(Original post by Mehrdad jafari)
Do you man the test charge in the equation I wrote? The direction of the field lines is independent of whether the test charge is positive or negative, but not on the force acting on the test charge in the field.
Do you man the test charge in the equation I wrote? The direction of the field lines is independent of whether the test charge is positive or negative, but not on the force acting on the test charge in the field.
what I meant to ask is that "Do we not always take the test charge to be positive?"
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Absent Agent
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#15
(Original post by Mihael_Keehl)
Sorry if i made it unclear lolzz, in your last line you said "even if the negative charge is the test charge."
what I meant to ask is that "Do we not always take the test charge to be positive?"
Sorry if i made it unclear lolzz, in your last line you said "even if the negative charge is the test charge."
what I meant to ask is that "Do we not always take the test charge to be positive?"
Edit: Mihael_Keehl: I think the reason that the electric field strength is defined with respect to a positive test charge in the field is that regardless of whether the point charge creating the field, in both case the positive test charge will accelerate along the field lines.
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langlitz
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#16
(Original post by Mehrdad jafari)
Well, me might take the positive charge to be the test charge in our examples, but what but I was referring to was when the negative charge was the test charge, in which case the negative test charge will move in the opposite direction to the field lines. I honestly don't see the reason as to why the electric field strength is defined with with respect to a positive test charge in the field that's not necessarily the case.
Edit: Mihael_Keehl: I think the reason that the electric field strength is defined with respect to a positive test charge in the field is that regardless of whether the point charge creating the field, in both case the positive test charge will accelerate along the field lines.
Well, me might take the positive charge to be the test charge in our examples, but what but I was referring to was when the negative charge was the test charge, in which case the negative test charge will move in the opposite direction to the field lines. I honestly don't see the reason as to why the electric field strength is defined with with respect to a positive test charge in the field that's not necessarily the case.
Edit: Mihael_Keehl: I think the reason that the electric field strength is defined with respect to a positive test charge in the field is that regardless of whether the point charge creating the field, in both case the positive test charge will accelerate along the field lines.
(Original post by Mihael_Keehl)
Sorry if i made it unclear lolzz, in your last line you said "even if the negative charge is the test charge."
what I meant to ask is that "Do we not always take the test charge to be positive?"
Sorry if i made it unclear lolzz, in your last line you said "even if the negative charge is the test charge."
what I meant to ask is that "Do we not always take the test charge to be positive?"
Why are people talking about test charges? It's much simpler than that. It's convention that the electric field points away from positive charge and towards a negative charge. It's like saying why does the magnetic field point from north to south, it's convention (although you can't have one pole on it's own of course)
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ChaoticButterfly
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Absent Agent
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#18
(Original post by langlitz)
Why are people talking about test charges? It's much simpler than that. It's convention that the electric field points away from negative charge and towards a positive charge. It's like saying why does the magnetic field point from north to south, it's convention (although you can't have one pole on it's own of course)
Why are people talking about test charges? It's much simpler than that. It's convention that the electric field points away from negative charge and towards a positive charge. It's like saying why does the magnetic field point from north to south, it's convention (although you can't have one pole on it's own of course)
Although I also believe it's much simpler, I don't think the convention itself was ruled out from nothing. I have not studied Maxwell's equations but I was reading that this was somehow related to the mathematics describing it in terms that field lines point away from the positive charge towards the negative charge, for which they have non-zero divergence at those points.
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langlitz
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#19
(Original post by Mehrdad jafari)
Yeah, I guess it was unnecessary talking about test charges but I was referring to when the force on a charge particle is in the opposite direction to the field lines, as in the case of a negative charge in the electric field.
Although I also believe it's much simpler, I don't think the convention itself was ruled out from nothing. I have not studied Maxwell's equations but I was reading that this was somehow related to the mathematics describing it in terms that field lines point away from the positive charge towards the negative charge, for which they have non-zero divergence at those points.
Yeah, I guess it was unnecessary talking about test charges but I was referring to when the force on a charge particle is in the opposite direction to the field lines, as in the case of a negative charge in the electric field.
Although I also believe it's much simpler, I don't think the convention itself was ruled out from nothing. I have not studied Maxwell's equations but I was reading that this was somehow related to the mathematics describing it in terms that field lines point away from the positive charge towards the negative charge, for which they have non-zero divergence at those points.
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langlitz
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#20
(Original post by Mihael_Keehl)
I understand the latter part: but with EFS isn't it always the positive charge that is causing the field?
I understand the latter part: but with EFS isn't it always the positive charge that is causing the field?
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