Physics
posted by Fred .
A portion of an electric circuit connected to a 7 ohm resistor is embedded in 1.20 kg of a solid substance in a calorimeter. The external portion of the circuit is connected to a 100 volt power supply.
(a) Assuming that all the heat generated by the resistor is absorbed by the solid substance, and that it takes 4 minutes to raise the temperature from 10 to 50 degrees C, calculate the specific heat for the substance.
(b) At 50 degrees C, the substance begins to melt. The heat of fusion is 4.5 x 10^5 joules per kilogram. How long after the temperature reaches 50 degrees C will it take for all of the substance to melt?

(a) Calculate the rate of heat transfer to the substance using
P = V^2/R. Multiply by 240 seonds for the number of Joules.
That energy divided by the mass and 60 C is the specific heat
(b) time required =
(Mass)(Heat of fusion)/(Power)
We will be happy to check your work