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Homework Help: Microwave and melting ice

  1. Feb 6, 2005 #1
    I have trouble figuring out the following question. Please help.
    Suppose you want to melt a piece of ice and boil the resulting water by using a microwave oven. The radiation is incident upon one side of the ice which has a cross sectional area of 0.00010 m^2. The microwave only heat the ice and not the glass container. The following data are given:
    Microwave wavelength: 0.122 m
    Peak Magnetic field of microwaves = 1.3 * 10^-5 T
    Ice is a cube with sides equal to 0.010 m
    Radiation is only incident upon one side of the ice.
    Mass of glass container = 0.20 kg
    Initial temperature of ice = 0 degree C

    How long do you need to run the Microwave Oven to melt the piece of ice and get the resultant water to boil (assume all heating goes into the water and the incident area remains constant).


    I calculated the requred heat is 1505.8 J. I thought of using Energy stored per unit volume equation (1/2 B^2/uo). However, I can't connect this result to the total energy required. I also tried to use E = hf. But it only gives me the energy of one photon.

    Thanks alot.
  2. jcsd
  3. Feb 6, 2005 #2


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    Staff Emeritus
    Science Advisor

    One has to calculate the mass of the ice and then multiply it by the specific energy required to melt the ice (solid to liquid - heat of formation) and raise it to boiling (0-100°C).

    The one has to determine the rate of energy deposition from the microwave system in order to determine the time.
  4. Feb 6, 2005 #3
    Thanks, Astronuc;
    I did figure out the energy required to melt ice and water from 0 to 100, which is 1505 J. However, I do have problem determining the rate of energy deposited from microwave. I couldn't find any time-related data (or I just didn't know it) so that it can be used in calculating the rate of energy.
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