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图示电路中,当滑动变阻器滑片向上滑动时,滑动变阻器接入电路中的阻值增大,则外电阻R增大,由闭合回路中的欧姆定律I=E/R+r,回路电流I减小,再由U_外=E-Ir,外电压U_外增大,因此电压表示数变大,由于回路电流减小,因此电阻R_1两端电压U_1减小,则电阻R_2两端分得电压U_2增大,流过电阻R_2的电流也增大,由并联分流可得,电流表示数减小.
In the circuit shown in the figure, the resistance of the sliding rheostat access circuit increases when the sliding vane of the sliding rheostat slides upward, and the external resistance R increases by Ohm’s law in the closed loop I = E / R + r, the loop current I decreases, then by U_ 外 = E-Ir, external voltage U_ external increases, so the voltage that the number becomes larger, because the loop current decreases, so the voltage across the resistor R_1 U_1 decreases, the resistor R_2 at both ends Divided by the voltage U_2 increases, the current flowing through the resistor R_2 also increases, shunt by shunt can be obtained, the number of current decreases.