QUESTION 16 A Gaussian sphere with radius 1.20 m encloses a point charge Q1 = +2.25E-6 C at the spherical center. The electric ux through the spherical surface is measured to be 251. Another point charge Q2 = +2.29E-6 C is placed at the point 1.00 m from the spherical center, and another point charge Q3 = 4.47E-6 C is placed at the point 1.50 m from the spherical center. Q1 remains at the spherical center. The electric ux through the spherical surface is then measured to be 452. What is @2/ @1? QUESTION 18 On the x axis, a point charge Q1 = -3.84E-6 C is placed at x = -1.60 m, and another point charge 92 = +6.51E-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 = -2.01E-6 C is placed at x = -1.60 m, and another point charge Q2 = -8.27E-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 5.85E-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)? 1.980000E6 QUESTION 22 Two parallel charged plates that are 0.173 m apart generate a uniform electric field E= 3.48E-3 N/C in between. A proton is initially at rest at one plate and is driven by the electric field to move toward the other plate. What is the proton's kinetic energy when it arrives at the other plate (in J)