InterviewSolution
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InterviewSolution
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A dipole with an electric moment p is located at a distance r from a along thread charge uniformly with a linear density `lambda`. Find the force F acting on the dipole if the vector p is oriented (a) along the thread (b) along the radius vector r (c ) at the right angles to the thread and the radius vector r. |
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Answer» Here, `E_(r) = (lambda)/(2pi epsilon_(0) r), E_(0) = E_(varphi) = 0` and `vec(F) = p (del vec(E))/(del l)` (a) `vec(p)` along the thread. `vec(E)` does not change as the point of observation is moved along the thread. (b) `vec(p)` along `vec(r)`, `vec(F) = F_(r) vec(e_(r)) = (lambda p)/(2pi epsilon_(0) r^(2)) vec(e_(r)) = (lambda vec(p))/(2pi epsilon_(0) r^(2))` (on using `(del)/(del r) vec(e_(r)) = 0`) (c) `vec(p)` along `vec(e_(theta))` `vec(F) = p (del)/(r del theta) (lambda)/(2pi epsilon_(0) r) e_(r)` `= (p lambda)/(2pi epsilon_(0) r^(2)) (del vec(e_(r)))/(del theta) = (p lambda)/(2po epsilon_(0)r^(2)) vec(e_(theta)) = (vec(p) lambda)/(2pi epsilon_(0) r^(2))` |
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