physics electric potential question...

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Abraham_Otaku
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I'll file the attachment below..
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Abraham_Otaku
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the answer to this is B, I understand that it should decrease, as the positive plate is at a higher potential, and closer to negative plate the potential decreases so its either B or D... but why B? why does it have to be linear? is there some equation that implies that it should be? like V=Ed?
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Stonebridge
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(Original post by Abraham_Otaku)
the answer to this is B, I understand that it should decrease, as the positive plate is at a higher potential, and closer to negative plate the potential decreases so its either B or D... but why B? why does it have to be linear? is there some equation that implies that it should be? like V=Ed?
...because in the question it says the field is uniform.
This means the electric field lines are parallel between the plates and the electric field (the value of E) doesn't change.
And yes, in a uniform field such as this E = V/d (This is the standard formula for the E field between 2 parallel plates.)
E is potential gradient and the gradient is constant because E is constant.
Hence a straight line graph of V against d.
It's a negative gradient here because you are going from + to -, as you rightly say, and V gets less as you move from + to -.
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Abraham_Otaku
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(Original post by Stonebridge)
...because in the question it says the field is uniform.
This means the electric field lines are parallel between the plates and the electric field (the value of E) doesn't change.
And yes, in a uniform field such as this E = V/d (This is the standard formula for the E field between 2 parallel plates.)
E is potential gradient and the gradient is constant because E is constant.
Hence a straight line graph of V against d.
It's a negative gradient here because you are going from + to -, as you rightly say, and V gets less as you move from + to -.
knew it had to do something with the fact that electric field is constant.. but in that case, doesn't that imply electric field strength is negative(as gradient would be -ve)?.. or is that something to do with direction of the electric field lines?..
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Stonebridge
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(Original post by Abraham_Otaku)
knew it had to do something with the fact that electric field is constant.. but in that case, doesn't that imply electric field strength is negative(as gradient would be -ve)?.. or is that something to do with direction of the electric field lines?..
Electric field strength is a vector and points from the + to the - plate: the direction that a positive charge experiences a force.
So yes, strictly speaking, it is defined as the negative potential gradient, because it points in the direction of decreasing electric potential.
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