题目

My brother Tom was very selfish when he was a little boy. He did not want share things with other people. For example, when he bought a chocolate cake, he put them in a secret place where I couldn’t find. Then he ate it all by himself. He never helped other. He said he is busy. That is, a game of tennis making him very busy. He did not care if something he did made people angrily. For instance, on one night he played strong and loudly music till four o’clock in the morning. But he is difference now. He often helps grandma with housework, helps mum with cooking and helps his classma20．如图，测定电源电动势和内电阻的实验中，电路连接正确，电流表和电压表量程选取合理．当电键闭合后，滑动变阻器滑片向右端移动时，接入电路的滑动变阻器阻值将变大（填“大”或“小”），电压表示数将变大（填“大’’或“小”）．