题目

Over 40 years ago, Walter Mischel, a psychologist, explored self-control in children with a simple but effective test. His test using the “marshmallow (棉花糖) test” laid the groundwork for the modern study of self-control.Mischel and his colleagues presented a preschooler with a plate of treats such as marshmallows. The child was then told that the researcher had to leave the room for a few minutes, and if the child waited until the researcher returned, she could have two marshmallows. If not, she would be allowed to eat only one marshmallow.In children as well as adults, willpower can小明利用如图甲所示的电路探究“电流跟电阻的关系”．已知电源电压为6V且保持不变，实验用到的电阻阻值分别为5Ω、10Ω、20Ω．（1））闭合开关后，发现电流表无示数，而电压表有示数，约为电源电压，原因可能是 ；（2）排除故障后，进行实验，实验中多次改变R的阻值， 调节滑动变阻器的滑片，使电压表示数保持不变，记下 电流表的示数，得到如图乙所示的电流随电阻R变化的图像；①由图像乙可以得出结论： ；②上述实验中，小明用5Ω的电阻做完实验后，然后将10Ω的电阻接入电路，闭合开关，电压表的示数将会 （选填“变大”、“变小”或“不变”），此时应该向 （选填“左”或“右”）移动滑片，使电压表示数为 V，然后读出电流表的示数；（3）实验室提供了三个不同规格的滑动变阻器：A：“30Ω 2A”，B：“50Ω 1A”，C：“100Ω， 0.1A”，要完成整个实验，应该选取滑动变阻器 （填代号）