Before the Spring Festival in Haikou this year, the weather was wet and cold. Xiaoming's mother bought an electric blanket for her grandparents. There are two electric blankets: high temperature and l

Before the Spring Festival in Haikou this year, the weather was wet and cold. Xiaoming's mother bought an electric blanket for her grandparents. There are two electric blankets: high temperature and low temperature. Solution:

(1)S should be in contact with 2. Therefore, when R is minimum and P is maximum in the circuit, when S touches point 2, R is short-circuited, and only R 0 works in the circuit (reasonable).

(2) ;

(3) , 。