1.5.9在图中,五个元件代表电源和负载。电流和电压的参考方向如图中所示。今通过实验测量得知I1 = -4A I2 = 6A I3 = 10AU1 = 140V U2 = -90V U3 = 60VU4 = -80V U5 = 30V1 试标出各电流的实际方向和各电压的实际极性。2 判断哪些元件是电源？哪些是负载？3 计算各元件的功率，电源发出的功率和负载取用的功率是否平衡？解：2、 元件1，2为电源；3，4，5为负载。3 、P1 = U1I1 = 140 * (-4)W = -560W P2 = U2I2 = (-90) * 6W = -540WP3 = U3I3 = 60 *10W = 600W P4 = U4I1 = (-80)* (-4)W = 320WP5 = U5I2 = 30 * 6W = 180W 电源发出功率PE =P1 + P2=1100W负载取用功率P = P3 + P4 + P5 = 1100W 两者平衡1.5.10在图中，已知I1 = 3mA,I2
