Examine the charge distribution shown in the following diagram. Three equal charges (+6.0 × 10¯³C) are placed at the vertices of an equilateral triangle with sides of 20 cm in length, as shown. a) If the charges were changed to -1.2 × 10-4C, how would the total electrical potential energy change? How do you know? b) If the charges were moved away from each other so they form an equilateral triangle with side lengths of 30 cm, how would the total electrical potential energy change? How do you know?

Two particles, with charges of 20.0 nC and 20.0 nC, are placed at the points with coordinates (0, 4.00 cm) and (0, 4.00 cm) as shown in Figure P20.19. A particle with charge 10.0 nC is located at the origin. (a) Find the electric potential energy of the configuration of the three fixed charges. (b) A fourth particle, with a mass of 2.00 1013 kg and a charge of 40.0 nC, is released from rest at the point (3.00 cm, 0). Find its speed after it has moved freely to a very large distance away.

The dielectric to be used in a parallel-plate capacitor has a dielectric constant of 3.60 and a dielectric strength of 1.60107 V/m. The capacitor has to have a capacitance of 1.25 nF and must be able to withstand a maximum potential difference 5.5 kV. What is the minimum area the plates of the capacitor may have?

An electronics technician wishes to construct a parallel plate capacitor using rutile ( = 100) as the dielectric. The area of the plates is 1.00 cm2. What is the capacitance if the rutile thickness is 1.00 mm? (a) 88.5 pF (b) 177 pF (c) 8.85 F (d) 100 F (e) 35.4 F

What is the maximum charge that can be stored on the 8.00-cm2 plates of an air-filled parallel-plate capacitor beforebreakdown occurs? The dielectric strength of air is 3.00 MV/m.

Four particles are positioned on the rim of a circle. The charges on the particles are +0.500 C, +1.50 C, 1.00 C, and 0.500 C. If the electric potential at the center of the circle due to the +0.500 C charge alone is 4.50 104 V, what is the total electric potential at the center due to the four charges? (a) 18.0 104 V (b) 4.50 104 V (c) 0 (d) 4.50 104 V (e) 9.00 104 V

A point charge of q=50108 C is placed at the center of an uncharged spherical conducting shell of inner radius 6.0 cm and outer radius 9.0 cm. Find the electric potential at (a) r = 4,0cm, (b) r = 8.0 cm, (c) r — 12.0 cm.

A long thin wire is used in laser printers to charge the photoreceptor before exposure to light. This is done by applying a large potential difference between the wire and the photoreceptor. a. Use Equation 26.23, V(r)=20lnRr to determine a relationship between the electric potential V and the magnitude of the electric field E at a distance r from the center of the wire of radius R (r R). b. Determine the electric potential at a distance of 2.0 mm from the surface of a wire of radius R = 0.80 mm that will produce an electric field of 1.8 106 V/m at that point.

Two charged particles with q1 = 5.00 C and q2 = 3.00 C are placed at two vertices of an equilateral tetrahedron whose edges all have length s = 4.20 m (Fig. P26.37). Determine what charge q3 should be placed at the third vertex so that the total electric potential at the fourth vertex is 2.00 kV. FIGURE P26.37

The labeled points in Figure 20.4 are on a series of equipotential surfaces associated with an electric field. Rank (from greatest to least) the work done by the electric field on a positively charged particle that moves from to , from to , from to , and from to . Figure 20.4 (Quick Quiz 20.2) Four equipotential surfaces.