InterviewSolution
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InterviewSolution
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State Gauss' theorem. With the help of this theorem, find out the electrical intensity at any nearby point due to a uniformly charged thin and long straight wire. Or, Define electrical dipole moment. An electrical dipole is placed within a uniform electric field (E) and is rotated to an angle angle(theta) = 180^(@). find out the work done. |
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Answer» Solution :Two equal andopposite charge`pm`q, SEPARATED by a DISTANCE vector `vec(l)` directed from -q to +q, from an electric dipole. Its dipole moment is `vec(p) = q vec(l)`. Torque on an electri dipole in an electric FIELD `vec(E)` is, `vec(tau) = vec(p) xx vec(E)`. Its magnitude is, `tau = p E SIN theta, ` where ` theta` = angle between `vec(p) and vec(E)`. `therefore` Work done to rotate the dipole from `0^(@)` to `180^(@)` is, W = `int DW = int_(0)^(180) tau d theta` = `p E int_(0)^(180) sin theta d theta = p E [ -cos theta]_(0)^(180) = 2pE` |
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