STOP TO THINK 26.1 Which potential graph describes the electric field at the left? y y y -x (a) (b) (C) (d) (e) FIGURE 26.16 Estimating the field and potential between two charged conductors. The field lines are perpendicular to the equipotential surfaces. 10 V OV 50 V 40 V 30 V 20 V The equipotential surfaces gradually change from the shape of one electrode to that of the other. EXAMPLE 26.6 Charging a capacitor The spacing between the plates of a 1.0 F capacitor is 0.050 mm. a. What is the surface area of the plates? b. How much charge is on the plates if this capacitor is charged to 1.5 V? MODEL Assume the capacitor is a parallel-plate capacitor. SOLVE a. From the definition of capacitance, dC A== 5.65 m 0 b. The charge is Q = CAV = 1.5 10 C = 1.5 C. ASSESS The surface area needed to construct a 1.0 F capacitor (a fairly typical value) is enormous. We'll see in Section 26.7 how the area can be reduced by inserting an insu- lator between the capacitor plates.