QUESTION 19 An initially charged capacitor is fully discharged in 1.51 s under a constant discharging current of 7.46E3 A. What is the charge initially stored in the capacitor (in C)? QUESTION 20 The resistivity of copper is 1.72E8 Q-m. We would like to use a copper wire to connect two devices that are 6.88 m apart and require the wire resistance to be no higher than 2.88E-3 Q. What is the minimum cross section area of the copper wire that we should use (in m2 )? QUESTION 21 Sustained current as small as 2.55E-6 A passing through the human heart can be fatal. Suppose a patient is undergoing open-heart surgery, and the patient's heart has a constant resistance of 2.80E2 Q. What is the minimum voltage across the heart that could pose a danger to the patient (in V)