A portion of an electric circuit connected to a 40-ohm resistor is embedded in .

Question

A portion of an electric circuit connected to a 40-ohm resistor is embedded in .2 kilogram of a solid substance in a calorimeter. The external portion of the circuit is connected to a 60-volt power supply.

A calculate the current in the resistor

b. Calculate the rate which heat is generated in the resistor

c. Assuming that all of the heat generated by the resistor is absorbed by the solid substance, and that it takes 4 minutes to raise the temperature of the substance from 20C to 80C, calculate the specific heat of the substance.

d. At 80C the substance begins to melt. The heat of fusion of the substance is 1.35X10^5 joules per kilogram. How long after the temperature reaches 80C will it take to melt all of the substance?

e. Draw a graph of the heating curve for the substance.

Explanation / Answer

a) P=I^2*R so I = sqrt(P/R)=1.22(A). b)it is 60 J per sec c) we have Q=P*T Q=m*C*(80-20). so that C=P*T/60m=1200(J/kgK) d)let it be t1 P*t1=m*1.35e5. so t1=450(sec). e) a straight line that go up (from T=20 to T=80) then a horizontal line. (at T=80)

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