(20 10? The circuit principle of electric drinking machine is shown in the figure. There are two working states: heating and heat preservation, which are automatically controlled by the internal tempe

(20 10? The circuit principle of electric drinking machine is shown in the figure. There are two working states: heating and heat preservation, which are automatically controlled by the internal temperature control switch S0. When (1)S0 is closed, R 1 and R2 are connected in parallel, and the resistance in the circuit reaches the minimum. According to the formula P=U2R, the electric power is the largest at this time, so the water dispenser is in a heating state.

Answer: When S0 is turned off, the water dispenser is in a heating state.

(2) When (2)S0 is turned off and there is only R2 in the circuit, the water dispenser is kept warm.

∫U = 220v, p guarantee =40W,

∴r2=u2p =(220v)240 w = 12 10ω。

A: The resistance of R2 is1210Ω.

(3)∵P plus =400W，t= 10min=600s，

∴Q=W=P plus t = 400w× 600s = 240000j.

Answer: The heat generated by heating 10 minute is 240,000 Joules.