生成这个题目的讲解---Here is the extracted content from the image: **Question 5** **Source:** 【2016 新课标 II】 **Question Stem:** 法拉第圆盘发电机的示意图如图所示。铜圆盘安装在竖直的铜轴上，两铜片 P、Q 分别与圆盘的边缘和铜轴接触，关于流过电阻 R 的电流，下列说法正确的是 () **Chart/Diagram Description:** * **Type:** A schematic diagram illustrating a Faraday disk generator connected to an external circuit. * **Main Elements:** * **Circular Disk:** A flat circular copper disk (铜圆盘) is shown horizontally. * **Central Shaft:** A vertical copper shaft (铜轴) is positioned at the center of the disk. The disk is mounted on this shaft. * **Rotation:** An curved arrow on the disk indicates its rotation direction around the central shaft. When viewed from above, this rotation is clockwise. * **Magnetic Field:** Several vertical arrows labeled 'B' indicate an upward uniform magnetic field passing through the disk. * **Contacts/Brushes:** * Point 'P' represents a copper brush/contact touching the edge of the circular disk. * Point 'Q' represents a copper brush/contact touching the central copper shaft. * **External Circuit:** A circuit connects the contacts P and Q: * Point P is connected to point 'b'. * Point Q is connected to point 'a'. * A resistor 'R' is connected between points 'a' and 'b'. * **Labels:** P, Q, R, B, a, b. * **Overall Setup:** The disk rotates within a magnetic field, and the generated current is collected by contacts P and Q and sent through an external resistor R. **Options:** * **A.** 若圆盘转动的角速度恒定，则电流大小恒定 * **B.** 若从上向下看，圆盘顺时针转动，则电流沿 a 到 b 的方向流动 * **C.** 若圆盘转动方向不变，角速度大小发生变化，则电流方向可能发生变化 * **D.** 若圆盘转动的角速度变为原来的 2 倍，则电流在 R 上的热功率也变为原来的 2 倍