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| Potential due to a Point Charge |
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| Consider two points 'a' and 'b' in an electrostatic field of a single isolated point charge +q. |
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| If a unit positive charge 'q' moves from 'a' to 'b' without acceleration, then the potential difference between 'a' and 'b' is given as |
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| = - Edl |
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| But dl = - dr |
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| [This is because when we move a distance 'dl' towards the source, we move in the direction of decreasing of 'r'] |
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| From equation (1), we have |
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| If the point 'a' is at infinity, then |
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| From the above, it is evident that for a given charge 'q', potential depends only on 'r'. Therefore, if the charge is positive, potential is positive and if the charge is negative, potential is negative. |
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