Hornework #5 ± Heating a Water Bath-MC ) 4 of 8 Constants Part A In the circuit

Question

Hornework #5 ± Heating a Water Bath-MC ) 4 of 8 Constants Part A In the circuit shown,(Figure 1) a 20-ohm resistor sits inside 104 g of pure water that is surrounded by insulating Styrofoam If the circuit's battery has an emf of 12 V and the wator is initially at temperature 10.3 °C, how long will it take for its temperature to rise to 590°C? Use 4190 J/kg·C" as the heat capacity of water, and oxpress your answer in seconds using three significant figures. View Available Hint(s) At 2947 Submit Incorrect:; Try Again Figure 1 of 1 10 10 Provide Feedback Next > 2012 10 10 WATER 512

Explanation / Answer

equivalent resistance

Req =20+5+[1/(10+10)+1/(10+10)+1/(5+5)]=30 ohms

Total current flowing in the circuit

I=V/Req =12/30=0.4 ohms

Power Dissipated in 20 ohms is

P=I2R=0.42*20=3.2 Watts

Heat required to raise temperature

Q=mC(T2-T1)=0.104*4190*(59-10.3)

Q=21221.5 J

Time required to raise the temperatue

t=Q/P=21221.5/3.2

t=6632 s

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