"Two electric dipoles of dipole moment p, and p, are placed at origin such that one is along x-axis and the P is P2 òther along y-axis respectively. If potential at point (r,0) is zero then (a) 1 (b) cot 0 (c) tan 0 (d) sin0.cos0

70 A slab of copper of thickness b = 2.00 mm is thrust into a parallel- plate capacitor of plate area A = 2.40 cm? and plate separation d = 5.00 f mm, as shown in Fig. 25-57; the slab is exactly halfway between the plates. (a) What is the capacitance after the slab is introduced? (b) If a charge q = 3.40 µC is maintained on the plates, what is the ratio of the stored energy before to that after the slab is inserted? (c) How much work is done on the slab as it is in- serted? (d) Is the slab sucked in or must it be pushed in? Figure 25-57 Problems 70 and 71.

(a) What is the potential difference (in V) between two points situated 14 cm and 28 cm from a 6.8 µC point charge? (Enter the magnitude.) V (b) To what location should the point at 28 cm be moved to increase this potential difference by a factor of two? O -18.7 cm from the 6.8 µC point charge 0.187 cm from the 6.8 µC point charge O infinity O 18.7 cm from the 6.8 µC point charge

What is the potential at point P?

A +38 µC point charge is placed 36 cm from an identical +38 µC charge. A –1.5 µC charge is moved from point A to point B as shown in Fig. 17–47. What is the change in potential energy? В 14 cm FIGURE 17-47 38 μC 12 cm 24 cm 38 μC Problem 81. A