This is my home. We have three bedrooms, a living room, a kitchen and a bathroom. In the kitchen, there is a fridge. The vegetables and fruit are in the fridge. The juice is in it, too. In my bedroom, there is a bed, a chair and a computer. Now I'm watching TV in the living room. Mum is cooking in the kitchen. My sister is taking a shower in the bathroom. Our cat is under my bed.

There are many____ ____in the____.

如图1所示的电路，电源电压保持不变，电阻R₁=10Ω．闭合开关S，变阻器滑片P从最右端滑到最左端的过程中，电压表示数U与电流表示数I的变化关系如图2中ab线段所示，由此可知：电源电压为　____ 　 V，变阻器R₂的最大阻值是　____ 　Ω．