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班級:光電一乙 姓名:施昶榆 學號:498L0090 98 學年度第 2 學期物理 Chap15 作業 1. Four point charges are situated at the corners of a square with sides of length a, as in Figure 1. Find the expression for the resultant force on the positive charge q. 設ｔ＝ 2. (a) Determine the electric field strength at a point 1.00 cm to the left of the middle charge shown in Figure 2. (b) If a charge of −2.00 μC is placed at this point, what are the magnitude and direction of the force on it? (a) (b) Ｆ＝Ｅｑ ＝ ＝－40Ｎ（40N 向左） Figure 2 3. In Figure 3, determine the point (other than infinity) at which the total electric field is zero. （先經過討論 => 只有可能在圖的左邊，而且是帶負電） =>6 =>3.5 (上一式乘 2)=>7 r= =左邊 1.82m(負不合) r Figure3 4. A point charge of +5.00 μC is located at the center of a sphere with a radius of 12.0 cm. Determine the electric flux through the surface of the sphere. 5. A small 2.00-g plastic ball is suspended by a 20.0-cm-long string in a uniform electric field, as shown in Figure 4. If the ball is in equilibrium when the string makes a 15.0° angle with the vertical as indicated, what is the net charge on the ball? m=2 E=1 g=9.8 T 為繩之張力 =>T T=2.031 N Figure 4 =>T =>5.256 q=5.256 =5.256