QUESTION 17 A Gaussian sphere with radius 1.20 m encloses a point charge Q1 = +5.27E-6 C at the spherical center. The electric flux through the spherical surface is measured to be P1. Now Q1 is removed, and another point charge Q2 = -4.88E-6 C is placed at the spherical center. The electric flux through the spherical surface is then measured to be P2. What is P2/ P1? QUESTION 18 On the x axis, a point charge Q1 = -6.31E-6 C is placed at x = -1.60 m, and another point charge Q2 = +1.83E-6 C is placed at x = +1.80 m. What is the electric potential at the origin, x = 0.00 m (in V; given that the zero potential is defined at the infinity of space)?QUESTION 19 On the x axis, a point charge Q1 = -6.94E-6 C is placed at x = -1.60 m, and another point charge O2 = -2.77E-6 C is placed at x = +1.80 m. What is the electric potential energy stored in this system (in J; given that the zero potential energy is defined when the two charges are infinitely far from each other)? QUESTION 20 An electron is initially placed 1.00E-11 m from a proton. An external force drives the electron to move at a constant speed to another position that is 3.20E-11 m from the proton. What is the work done by the external force on the electron (in J)? QUESTION 21 An infinitely large charged plate is placed at the y-z plane. The charge density on the plane is -4.44E-6 C/m2. The zero electric potential is defined on the charged plate. What is the electric potential at the position x = 7.88 m (in V)?QUESTION 22 Two parallel charged plates that are 0.173 in apart generate a uniform electric eld E = 2.10E3 N/C in between. A proton is initially at rest at one plate and is driven by the electric eld to move toward the other plate. What is the proton's kinetic energy when it arrives at the other plate (in J)