Supercapacitors have very large capacitance (typically from 0.1 to \(135 \mathrm{kF}\) ), small sizes, and very long charge-holding times, making them useful in nonbattery backup power applications. The charge-holding quality of a supercapacitor is measured using the circuit in Figure P7-66. The switch is closed for a long time (say, \(24 \mathrm{~h}\) ) and the capacitor charged to \(5 \mathrm{~V}\). The switch is then opened and the capacitor allowed to self-discharge through any leakage resistance for \(24 \mathrm{~h}\). Suppose that after \(24 \mathrm{~h}\) the voltage across a 100-F supercapacitor is \(475 \mathrm{~V}\). What is the equivalent leakage resistance in parallel with the capacitor?

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5 V (+1) 100 92 Supercapacitor + RL