(2014?Benxi model) Soymilk machine is a common appliance in modern families, such as the figure is a Nepal a soybean milk machine working principle of the circuit diagram (soybean milk machine has grinding cooking) (1) Soybean milk machine in the grinding state, the motor must be connected to the circuit, S2 closed, R1 is short-circuited, R2 and the motor is connected in parallel, the voltage is equal to the supply voltage, grinding and cooking at the same time heating,

Then the heating of soybean milk through the R2 current I=

P heating

U

=

1000W

220V

=4.5A;

(2) When this soymilk machine is in the holding state, it will work for 10 minutes, and the power consumed by the machine, W Holding=P Holding t=100W×10×60s=6×104J;

(3) The mass of the 1L of soymilk, m=ρSoymilkV= 1.0×103kg/m3×10-3m3=1kg,

Heating 1L of soymilk from 30℃ to 90℃ needs to absorb heat Q suction=cm(t-t0)=4.0×103?J/(kg?℃)×1kg×(90℃-30℃)=2.4×105J;

Electricity consumed by soymilk maker W heating=

Q Suck

η

=

2.4×105?J

80%

=3×105J,

Needed to heat up time tHeat up=< table cellpadding="-1" cellspacing="-1" style="margin-right:1px">W HeatingP Heating=

3×105J

1000W

=300s.

Answer: (1) the soybean milk machine is in the state of grinding and cooking, heating soybean milk through the current of R2 is 4.5A;

(2) the soybean milk machine in the state of heat preservation, work for 10 minutes, the soybean milk machine consumes 6 × 104J;

(3) 1L of soybean milk from 30 ℃ to 90 ℃ needs to absorb heat. (3) heating 1L of soybean milk from 30 ℃ to 90 ℃ need to absorb heat 2.4 × 105J; if the heating efficiency is 80%, it takes 300s.