Dielectric heating, also known as RF or high frequency heating, is a process in which a high-frequency alternating electric field or microwave electromagnetic radiation heats a dielectric material. An important application of this phenomenon is in the heating of food in a microwave oven. Microwave ovens heat food by bombarding it with electromagnetic radiation in the microwave spectral range, causing polarized molecules in the field to rotate and build up thermal energy, thus cooking or heating the food. However, when the food is initially frozen, because the molecules in the solid do not rotate readily, volumetric heat generation is an order of magnitude less than if the material were in the liquid form. Microwave power not absorbed in the food is dissipated to the microwave generator in the form of heat. Estimate the time it takes to heat a 1 kg roast, initially at a temperature of – 20°C, after it is placed in a 1-kW total power micros-wave oven with an interior temperature of 30°C. Assume the meat has a spherical shape and a heat transfer coefficient of 12 W/m²•K from its surface. First estimate the time required to reach a uniform temperature of 0°C when the water in the meat is in the form of ice. Assume that 4% of the oven power is absorbed in the food. After the meat thaws (all ice is melted), the meat increases in temperature. Now estimate the time required for the meat to reach 75°C if 90% of the microwave oven power is absorbed in the meat. Assume that the physical properties of meat are the same as those of liquid water.