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《高中物理》下册第二章练习六的第四题,提出了惠斯通电桥中I_g的有无及方向问题。这个问题可有多种解法。本文就其中的一种解法作了较详细的讨论,供选学者参考。设惠斯通电桥中四个电阻 R_1、R_2、R_3、R_4为已知,且电桥未达到平衡状态,此时,必有电流通过电流表。若以I_g表示这一电流,U_1、U_2、U_3、U_4分别表示R_1、R_2、R_3、R_4两端的电压,则: U_1/U_2=I_1R_1/I_2R_2, U_3/U_4=I_3R_3/I_4R_4 U_1/U_1+U_2=I_1R_1/I_1R_1+I_2R_2,
The fourth question in the sixth chapter of the second volume of the “secondary school physics” physics questions the question of the existence and direction of I_g in the Wheatstone bridge. There are many solutions to this problem. This article makes a detailed discussion of one of the solutions to the selection of scholars. Assume that the four resistors R_1, R_2, R_3, and R_4 in the Wheatstone bridge are known and the bridge has not reached equilibrium. At this time, there must be current through the ammeter. If this current is represented by I_g, U_1, U_2, U_3, U_4 represent voltages across R_1, R_2, R_3, R_4, respectively: U_1/U_2=I_1R_1/I_2R_2, U_3/U_4=I_3R_3/I_4R_4 U_1/U_1+U_2 =I_1R_1/I_1R_1+I_2R_2,