Question

Please draw pictures!

33. . (II) Calculate the electric potential due to a dipole whose dipole moment is 4.2 × 10-30 C . m at a point 2.4 x 10m away if this point is (a) along the axis of the dipole nearer the positive charge: (b) 45° above the axis but nearer the positive charge; (c) 45° above the axis but nearer the negative charge.

Answer 1

An electric potential due to a dipole which will be given by -

V = k_e p cos $\theta$ / r²

(a) If this point along the axis of dipole nearer the positive charge, then we get

V = (9 x 10⁹ Nm²/C²) (4.2 x 10^-30 C.m) cos 0⁰ / (2.4 x 10^-9 m)²

V = [(3.78 x 10^-20 Nm³/C) / (5.76 x 10^-18 m²)]

V = 6.56 x 10^-3 V

(b) If this point is 45⁰ above the axis but nearer the positive charge, then we get

V = (9 x 10⁹ Nm²/C²) (4.2 x 10^-30 C.m) cos 45⁰ / (2.4 x 10^-9 m)²

V = [(2.672838 x 10^-20 Nm³/C) / (5.76 x 10^-18 m²)]

V = 4.64 x 10^-3 V

(c) If this point is 45⁰ above the axis but nearer the negative charge, then we get

V = (9 x 10⁹ Nm²/C²) (4.2 x 10^-30 C.m) cos 135⁰ / (2.4 x 10^-9 m)²

V = [(-2.672838 x 10^-20 Nm³/C) / (5.76 x 10^-18 m²)]

V = - 4.64 x 10^-3 V