Fundamentals of Physics 8/e 24 - Finding the Electric Potential D. Halliday, R. Resnick, and J. Walker 國立彰化師大教學卓越計畫 理學院普通物理整合型教材 主持人：郭艷光院長

彰化師大教學卓越－普物教材－理學院長郭艷光主持 Outline 24-1 What Is Physics? 24-2 Electric Potential Energy 24-3 Electric Potential 24-4 Equipotential Surfaces 24-5 Calculating the Potential from the Field 24-6 Potential Due to a Point Charge 24-7 Potential Due to a Group of Point Charges 24-8 Potential Due to an Electric Dipole 24-9 Potential Due to a Continuous Charge Distribution 24-10 Calculating the Field from the Potential 24-11 Electric Potential Energy of a System of Point Charges 24-12 Potential of a Charged Isolated Conductor 彰化師大教學卓越－普物教材－理學院長郭艷光主持

彰化師大教學卓越－普物教材－理學院長郭艷光主持 24-1 What Is Physics? In this chapter we will define the electric potential (symbol V) associated with the electric force. 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-2 Electric Potential Energy x . xi xf F(x) 彰化師大教學卓越－普物教材－理學院長郭艷光主持

彰化師大教學卓越－普物教材－理學院長郭艷光主持 24-3 Electric Potential 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-4 Equipotential Surfaces For path Ⅰ: WⅠ=0 because ΔV = 0 For path Ⅱ: WⅡ=0 because ΔV = 0 For path Ⅲ: WⅢ= qΔV= q( V₂－V₁) For path Ⅳ: WⅣ= qΔV= q( V₂－V₁) Note: When a charge is moved on an equipotential surface (ΔV = 0) The work done by the electric field is zero: W=0 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-4 Equipotential Surfaces B  V q W=0. Thus: qE Δr cosθ = 0 q ≠0, E≠0, Δr ≠ 0 Thus: cosθ = 0 → θ = 90˚ The correct picture is shown in the figure below. S V 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-4 Equipotential Surfaces 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-5 Calculating the Potential from the Field B 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-6 Potential Due to a Point Charge 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-7 Potential Due to a Group of Point Charges q1 q3 q2 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-8 Potential Due to an Electric Dipole 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-9 Potential Due to a Continuous Charge Distribution . P r dq For a volume charge distribution dq = ρdV For a surface charge distribution dq = σdA For a linear charge distribution dq = λdl 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-9 Potential Due to a Continuous Charge Distribution dq O A 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-10 Calculating the Field from the Potential 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-11 Electric Potential Energy of a System of Point Charges x y O q1 q2 q3 r12 r23 r13 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-11 Electric Potential Energy of a System of Point Charges x y  q1 Step 1 Step 1: Step 2: x y O r12 q1 q2  Step 2 Step 3: Step 3 x y O r12 r13 r23 q1 q2 q3  彰化師大教學卓越－普物教材－理學院長郭艷光主持 (24 - 16)

24-12 Potential of a Charged Isolated Conductor path A B conductor 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-12 Potential of a Charged Isolated Conductor 彰化師大教學卓越－普物教材－理學院長郭艷光主持

24-12 Potential of a Charged Isolated Conductor 彰化師大教學卓越－普物教材－理學院長郭艷光主持

彰化師大教學卓越－普物教材－理學院長郭艷光主持 End of chapter 24! 彰化師大教學卓越－普物教材－理學院長郭艷光主持