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Figure (a) and (b) show the field lines of a positive and negative point charge respectively. (a) Give the signs of the potential difference . V_(p)-V_(Q), V_(B)-V_(A) (b) Give the sign of the potential energy difference if a small negative charge is moved from points Q to P from point A to B.(c) Give the sign of the work done by the field in moving a small positive charge from Q to P. ( d) Give the sign of the work done by the external agency in moving a samall negative charge from B to A . (e ) Does the kinetic energy of a small negative charge increase or decrease in going from B to A ? |
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Answer» Solution :A small negative charge will be attracted towards positive charge. The negative charge moves from higher potential energy to lower potential energy . Therefore the sign of potential energy difference from Q to P is negative. Similarly `(PE)_(A) gt ( PE)_(B)` and hence sign of potential energy difference is negative. ( c) In moving a small positive charge from Q to P work to be DONE by an external agency against the ELECTRIC FIELD . Therefore work done by the field is negative . (d) In moving a small negative charge from B to A work has to be done by the external agency It is positive. ( e) Due to force of repulsion on the negative charge VELOCITY decreases and hence the kinetic energy decreases in going from B to A. |
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