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  1. #1 what this means? 
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    http://www.cco.caltech.edu/~phys1/ja...ingCharge.html
    "As time goes on, the line becomes more and more perpendicular, the horizontal component increasing faster than the vertical component"
    Which is that horizontal and which vertical component?
    Please help me. Thank you.


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  3. #2  
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    The link you gave doesn't appear to work.

    Regards


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    try this link

    http://www.cco.caltech.edu/~phys1/ja...ingCharge.html

    When the charge moves at relativistic speed, the electric field is concentrated near the pole, and consequently the field lines are shifted. The field lines always point to where the charge is at that instant, if we are within the current sphere of information. If that charge has changed speed or direction within a time t < r/c, where r is the distance away, and c is the speed of light, we will not know that charge has accelerated, and the field lines will still point to where the charge would be if it hadn't changed speed or direction.

    Notice That when the charge is accelerated, because the field lines must be continuous, it is forced in a direction almost perpendicular to the the direction of propogation. As time goes on, the line becomes more and more perpendicular, the horizontal component increasing faster than the vertical component. Associated with this electric field is a magnetic field, perpendicular to the electric field and the direction of propogation, which describes light.
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  5. #4  
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    Quote Originally Posted by Harold14370
    try this link

    http://www.cco.caltech.edu/~phys1/ja...ingCharge.html

    When the charge moves at relativistic speed, the electric field is concentrated near the pole, and consequently the field lines are shifted. The field lines always point to where the charge is at that instant, if we are within the current sphere of information. If that charge has changed speed or direction within a time t < r/c, where r is the distance away, and c is the speed of light, we will not know that charge has accelerated, and the field lines will still point to where the charge would be if it hadn't changed speed or direction.

    Notice That when the charge is accelerated, because the field lines must be continuous, it is forced in a direction almost perpendicular to the the direction of propogation. As time goes on, the line becomes more and more perpendicular, the horizontal component increasing faster than the vertical component. Associated with this electric field is a magnetic field, perpendicular to the electric field and the direction of propogation, which describes light.
    Which is that horizontal component and which vertical?
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  6. #5  
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    Thank you Harold.

    I must confess that, like Scientist91, I find the description rather obscure. For example,

    .. when the charge is accelerated, because the field lines must be continuous, it is forced in a direction almost perpendicular to the direction of propogation. As time goes on, the line becomes more and more perpendicular, the horizontal component increasing faster than the vertical component.

    it isn't clear what is forced in a direction almost perpendicular to the direction of propagation. I think what it is referring to is that the electric field lines, instead of spreading out radially from the charge, develop a "kink" if the charge suddenly accelerates, and that this kink propagates outwards away from the charge at the speed of light. (Field lines that are along the direction of acceleration - horizontal in the applet - will not have a kink in them and there will be no radiation in this direction.)

    For a charge that isn't moving, the electric field is entirely radial. For a charge that is accelerating, the field lines will have a component perpendicular to the radial direction (except for those field lines along the direction of acceleration). I think it is this component that is being referred to in the statement [i]the line becomes more and more perpendicular[I] .
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    Quote Originally Posted by Old Fool
    Thank you Harold.

    I must confess that, like Scientist91, I find the description rather obscure. For example,

    .. when the charge is accelerated, because the field lines must be continuous, it is forced in a direction almost perpendicular to the direction of propogation. As time goes on, the line becomes more and more perpendicular, the horizontal component increasing faster than the vertical component.

    it isn't clear what is forced in a direction almost perpendicular to the direction of propagation. I think what it is referring to is that the electric field lines, instead of spreading out radially from the charge, develop a "kink" if the charge suddenly accelerates, and that this kink propagates outwards away from the charge at the speed of light. (Field lines that are along the direction of acceleration - horizontal in the applet - will not have a kink in them and there will be no radiation in this direction.)

    For a charge that isn't moving, the electric field is entirely radial. For a charge that is accelerating, the field lines will have a component perpendicular to the radial direction (except for those field lines along the direction of acceleration). I think it is this component that is being referred to in the statement [i]the line becomes more and more perpendicular[I] .
    .. when the charge is accelerated, because the field lines must be continuous, it is forced in a direction almost perpendicular to the direction of propogation. As time goes on, the line becomes more and more perpendicular, the horizontal component increasing faster than the vertical component.
    it refers to the electric field:- "The electric field (it) is forced...".
    This part "As time goes on, the line becomes more and more perpendicular" is very obscure because always the electric field lines are perpendicular to the direction of motion. Also this part "the horizontal component increasing faster than the vertical component", I don't know what this refers to? Is it refering to the horizontal and vertical component of the line or what?
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    Scientist91,

    ..always the electric field lines are perpendicular to the direction of motion.

    I can't understand why you think this is the case. The electric field lines spread out radially from the charge and some are actually in the direction of motion. I think the word perpendicular is used in the sense of perpendicular to the direction that a field line would have if the charge was not accelerating.

    Also this part "the horizontal component increasing faster than the vertical component", I don't know what this refers to? Is it refering to the horizontal and vertical component of the line or what?

    I think it is referring to the components of the "kink" in a field line. However, I don't find it a particularly transparent account.
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    Quote Originally Posted by Old Fool
    Scientist91,

    ..always the electric field lines are perpendicular to the direction of motion.

    I can't understand why you think this is the case. The electric field lines spread out radially from the charge and some are actually in the direction of motion. I think the word perpendicular is used in the sense of perpendicular to the direction that a field line would have if the charge was not accelerating.

    Also this part "the horizontal component increasing faster than the vertical component", I don't know what this refers to? Is it refering to the horizontal and vertical component of the line or what?

    I think it is referring to the components of the "kink" in a field line. However, I don't find it a particularly transparent account.
    Sorry, but what is "kink"?
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    Sorry, but what is "kink"

    Going back to the applet shown in the link that Harold gave, if you click on "Go" and then change the speed of the particle (cause it to accelerate) by clicking on the scale which I think is marked "v", you will see sharp bends appear in the field lines, and these bends moves outwards away from the charge. Such a bend, I have described as a "kink".
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  11. #10  
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    Quote Originally Posted by Old Fool
    Sorry, but what is "kink"

    Going back to the applet shown in the link that Harold gave, if you click on "Go" and then change the speed of the particle (cause it to accelerate) by clicking on the scale which I think is marked "v", you will see sharp bends appear in the field lines, and these bends moves outwards away from the charge. Such a bend, I have described as a "kink".
    But the horizontal component is not incresing, Infact, it is reducing its self.
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    I agree that the use of the terms "horizontal" and "vertical" is confusing. The bend (or kink) in a field line appears to approach a right angle as it propagates outwards.

    (Note: in order to see these effects in the applet, I have to click on the v scale itself rather than on the buttons at either end of it)
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    I think horizontal means from left to right on the screen, and vertical means bottom to top.

    If you click the mouse button on the slider, you will create a step change in the velocity, call it Delta-V, and you will make a kink in the field line. The outer straight segment of the field line points to where the charge would have been continuing at its speed before the step change in velocity. The inner segment points to where it is. The difference between where it is and where it would have been is Delta-V times time, which increases with time. So the line connecting the two straight segments approaches a perpendicular to the straight segments over time. This is best seen on the field line that goes vertically from the charge.

    Don't ask me why the author of the applet feels this is significant. I'm not smart enough to figure that part out.
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