Solution of Problem point

W E definition : 4 point Gauss’s law : 2point + result range each 0.5 point (total 1 point) Relationship between D and E : 2 point + result range each 0.5 point (total 1 point)

V definition : 2 point Get V : 2 point Get W : 2 point Solution 1 : 10 point Answer : 4 point

Solution 2 : 10 point Equation 3 point (range -1, wrong D or E, -1) calculation 3 point (range -1, wrong D or E, -1)

Solution of Problem point

Declare formula : 10 point r = za z = 0.04, r’ = pa p Calculate : 3 point Answer : 4 point 2.48 V equation : 3 point

Solution of Problem 3.a 10 point

Declare definition : 2 point Calculate voltage affect to charges : 2 point (result 1 point) Declare formula : 2 point Calculate total energy using symmetric property : 2 point Answer : 2 point Solution using below also be permitted. (It is proved to be correct.)

Solution of Problem 3.b 10 point

Calculate total energy : 4 point (result 2 point) Calculate total energy using superposition principle : 4 point (result 2 point) Answer : 2 point Solution using below also be permitted. (It is proved to be correct.)