đặt lần lượt các điện tích q1=1nC, q2=-1nC, q3=1nC, q4=1nC vào các đỉnh A, B, C ,D của hình chữ nhật, kích thước 20cm x 40cm trong không khí. Tính điện thế tại O là giao điểm của 2 đường chéo hình chữ nhật, chọn góc điện thế tại vô cùng.

In this experiment, you will use a track, a toy car, and some washers to explore newton’s first two laws of motion. you will make observations and collect data regarding the motion of these objects. in the space below, write a general scientific question that you will answer by doing this experiment.

Copper has free electrons per cubic meter. a 71.0-cm length of 12-gauge copper wire that is 2.05 mm in diameter carries 4.85 a of current. (a) how much time does it take for an electron to travel the length of the wire? (b) repeat part (a) for 6-gauge copper wire (diameter 4.12 mm) of the same length that carries the same current. (c) generally speaking, how does changing the diameter of a wire that carries a given amount of current affect the drift velocity of the electrons in the wire?

Follow these directions and answer the questions. 1. set up the ripple tank as in previous investigations. 2. bend the rubber tube to form a "concave mirror" and place in the ripple tank. the water level must be below the top of the hose. 3. generate a few straight pulses with the dowel and observe the reflected waves. do the waves focus (come together) upon reflection? can you locate the place where the waves meet? 4. touch the water surface where the waves converged. what happens to the reflected wave? 5. move your finger twice that distance from the hose (2f = c of c, center of the curvature) and touch the water again. does the image (the reflected wave) appear in the same location (c of c)? you may have to experiment before you find the exact location. sometimes it is hard to visualize with the ripple tank because the waves move so quickly. likewise, it is impossible to "see" light waves because they have such small wavelengths and move at the speed of light. however, both are examples of transverse waves and behave in the same way when a parallel wave fronts hit a curved surface.