在如图所示的电路中,\(R_{1}\)、\(R_{2}\)、\(R_{3}\)和\(R_{4}\)皆为定值电阻,\(R_{5}\)为可变电阻,电源的电动势为\(E\),内阻为\(r\),设电流表\(A_{1}\)的读数为\(I_{1}\),电流表\(A_{2}\)的读数为\(I_{2}\),电压表\(A_{1}\)的示数为\(U_{1}\),电压表\(V_{2}\)的读数为\(U_{2}\),当\(R_{5}\)的滑动触点向\(a\)端移动过程中,电流表\(A_{1}\)的读数变化量大小为\(\triangle I_{1}\),电流表\(A_{2}\)的读数变化量大小\(\triangle I_{2}\),电压表\(V_{1}\)的读数变化量大小为\(\triangle U_{1}\),电压表\(V_{2}\)的读数变化量大小为\(\triangle U_{2}\),则\((\) \()\)