详细分析解答截图题目，说明用到的知识点和解答本题的易错点---**Question 17** **Question Stem:** 17. 某兴趣小组利用铜片、锌片和橘子制作了水果电池, 并用数字电压表 (可视为理想电压表) 和电阻箱测量水果电池的电动势 E 和内阻 r, 实验电路如图 1 所示。连接电路后, 闭合开关 S, 多次调节电阻箱的阻值 R, 记录电压表的读数 U, 绘出图像, 如图 2 所示, 可得: 该电池的电动势 E = _______ V, 内阻 r = _______ kΩ。(结果保留两位有效数字) *(Translation: 17. An interest group made a fruit battery using copper plates, zinc plates, and an orange, and measured the electromotive force E and internal resistance r of the fruit battery using a digital voltmeter (which can be considered an ideal voltmeter) and a resistance box. The experimental circuit is shown in Figure 1. After connecting the circuit, close switch S, adjust the resistance of the resistance box R multiple times, record the voltmeter reading U, and plot the graph, as shown in Figure 2. It can be obtained: The electromotive force of this battery E = _______ V, internal resistance r = _______ kΩ. (Keep two significant figures for the result))* **Figure 1 Description:** * **Type:** Circuit diagram. * **Elements:** * A voltage source labeled E and r, representing the fruit battery with electromotive force E and internal resistance r. The positive terminal is on the left. * A switch labeled S, shown in the open position. * A variable resistor labeled R. * A voltmeter labeled V, connected in parallel with the variable resistor R. * **Connections:** The voltage source, switch S, and variable resistor R are connected in series, forming a closed loop when S is closed. The voltmeter V is connected in parallel across the variable resistor R. * **Labels:** E, r, S, R, V. **Figure 2 Description:** * **Type:** Line chart (graph). * **Axes:** * Y-axis: Labeled U/V (Voltage in Volts). The scale runs from 0.3 to 1.1 V in increments of 0.1 V, with finer grid lines every 0.02 V. * X-axis: Labeled U/R (with the unit indicated as $10^{-6}$ A). The scale runs from 0 to 200 in increments of 20, with finer grid lines every 4. The unit is $(10^{-6} \text{ A})$. * **Data Series:** A single straight line is plotted, sloping downwards from left to right. * **Key Points:** * The line intersects the Y-axis (where U/R = 0) at U = 1.0 V. * The line passes through approximately U = 0.8 V at U/R = 60. * The line passes through approximately U = 0.6 V at U/R = 120. * The line ends at approximately U = 0.3 V at U/R = 200. * **Interpretation:** The graph plots the external voltage U against the current I, where the current is represented by U/R. The relationship is linear, representing the equation $U = E - Ir$. Since $I = U/R$, the equation is $U = E - r(U/R)$. This confirms the y-intercept is E and the slope is -r. **Calculation based on graph:** * Electromotive force E: From the y-intercept of the graph (where U/R = I = 0), U = E. The graph intercepts the y-axis at U = 1.0 V. So, E = 1.0 V. * Internal resistance r: The slope of the graph is $\frac{\Delta U}{\Delta (U/R)} = -r$. Using points (0, 1.0) and (200, 0.3): Slope = $\frac{0.3 - 1.0}{200 - 0} = \frac{-0.7}{200}$. The x-axis unit is $10^{-6} \text{ A}$. So, Slope = $\frac{-0.7 \text{ V}}{200 \times 10^{-6} \text{ A}}$. $-r = \frac{-0.7}{200 \times 10^{-6}} \Omega$. $r = \frac{0.7}{200 \times 10^{-6}} \Omega = \frac{0.7}{2 \times 10^{-4}} \Omega = 0.35 \times 10^4 \Omega = 3500 \Omega$. The question asks for r in kΩ. $3500 \Omega = 3.5 \text{ k}\Omega$. * Rounding to two significant figures: E = 1.0 V, r = 3.5 kΩ. **Answer Format:** E = _______ V, 内阻 r = _______ kΩ。 **Extracted Content:** 17. 某兴趣小组利用铜片、锌片和橘子制作了水果电池, 并用数字电压表 (可视为理想电压表) 和电阻箱测量水果电池的电动势 E 和内阻 r, 实验电路如图 1 所示。连接电路后, 闭合开关 S, 多次调节电阻箱的阻值 R, 记录电压表的读数 U, 绘出图像, 如图 2 所示, 可得: 该电池的电动势 E = _______ V, 内阻 r = _______ kΩ。(结果保留两位有效数字) 图 1: [Circuit diagram showing a voltage source (E, r), switch (S), variable resistor (R), and voltmeter (V) across R.] 图 2: [Graph with Y-axis U/V and X-axis U/R ($10^{-6}$ A), showing a downward sloping straight line from (0, 1.0) to (200, 0.3).]