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Question
A point charge +Q is placed at point O, as shown in the figure. Is the potential difference VA – VB positive, negative or zero?
Solution
Electric potential at a distance r from the point charge +Q is given by
`V(r) = 1/(4πε_0) Q/R`
Potential at point A will be
`V(r_A) = 1/(4πε_0) Q/r_A`
Similarly, potential at point B will be
`V(r_B) = 1/(4πε_0) Q/r_A`
`because r_A < r_B`
`therefore V_A > V_B`
`therefore V_A - V_B > 0`
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