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一、问题与探究1.问题在闭合电路中,电源电动势为E,内阻为r,外电路电阻为R,电源的输出功率随外电阻如何变化?满足什么条件输出功率最大?如果电路中含有电动机情况又如何?2.探究(1)函数分析法对于任意电路,电源的输出功率P=UI=EI-I~2r=P_总-P_内对于纯电阻电路电源的输出功率P=UI=(E/(R+r))~2R经配方整理得P=E~2/(R-r)~2/R+4r由此可以看出,输出功率与外电阻的关系:当R=r时,电源的输出功率最大,且最大值P_m
First, the problem and exploration 1. Problem In the closed circuit, the power electromotive force E, the internal resistance of r, the external circuit resistance R, the power output power with the external resistance how to change? Meet the conditions of the maximum output power? If the circuit contains (1) Function Analysis Method For any circuit, the output power of the power supply P = UI = EI-I ~ 2r = P_ total-P_ for the output power of purely resistive circuit power supply P = UI = (E / (R + r)) ~ 2R formulated by the formula P = E ~ 2 / (Rr) ~ 2 / R + 4r It can be seen that the output power and external resistance: when R = r , The power output power maximum, and the maximum value P_m