Toast is toast "burn baby burn, disco inferno!"
I also found this on my computer.
The Concept. The purpose of this experiment is to calculate an estimated value for the emissivity of bread at the moment it becomes toast. Emissivity is described as a coefficient that is used to define the ratio of heat transfer that an object receives from a given black body. In the following experiment, the heating device on the toaster is assumed to be a black body, or a body that absorbs all light energy transferred to it. The heating device cannot possibly be a black body, but it can be assumed as such for the purposes of this experiment.
The Method. The black body (toaster) transfers heat to the non-black body (the bread) at a rate defined by the emissivity of the bread. The relation between emissivity and rate of heat transfer is defined in Stefan-Boltzman’s law:
Q = AF (T14- T24)
Where:
Q = The max rate of transfer the black body can supply
= The Emissivity of the toast (non-black body)
A = The surface area of the bread being toasted
F = View factor, a ratio of the area of the heating surface to that of the surface being heated
= Stefan - Boltzman’s Constant
T1 = Temperature of heating element
T2 = Temperature of bread slice before being heated (room temperature)
Before utilizing this equation, however, it must be defined as to what actually constitutes toast. The emissivity of bread before being heated is a different value than the emissivity of a well-toasted piece of bread. A specific point of the heating process must then be chosen to find the emissivity at that given point. The goal is to find the emissivity at the exact point that bread becomes toast. That point, however, is subjective. No point can specifically be designated as the point at which bread becomes toast. In light of this subjectivity, the aforementioned point of toast must be assumed. This loop-hole of sorts only affects the Q value in Stefan - Boltzman’s law, however, all other values of the law (excluding emissivity) are either given or easily measured.
When Bread Becomes Toast. To discover the point at which bread becomes toast, a touch test of four slices of bread at different heated levels is implemented. Through the course of the test, it is agreed that a power setting of “4” on the toaster is the setting at which bread becomes toast. Unfortunately the mechanics of the power distribution at different settings on the toaster are unknown. The power rating displayed on the bottom of the toaster is that of 0.4 Kilowatts. Since it is unknown whether or not the 4th setting is a percentage of the total power or another function of the total power (i.e. time), 0.4 is assumed to be the power of the toaster. Outside of the experiment, lighter colored objects would require more power to heat to the same level as the toast and darker colored objects would not require as much as 0.4 Kilowatts, thus differentiating emissivities between objects.
Calculating Emissivity. To use the 0.4 Kilowatt measurement of power it must be converted into units that coincide with Stefan - Boltzman’s constant. Power units of Btu/hr (British Thermal Units per hour) are necessary. Temperature must also be in terms of the constant. Fortunately, both room temperature and the temperature of the heating element when energized are given in such terms. Area is easily measured in feet and the view factor is simply a ratio of this area to the are of the heating element. All values of Stefan-Boltzman’s law are then defined, with the exception of emissivity. Left with only one variable, emissivity is far from difficult to calculate.
Hahahahahaha hah haaaaaa.
The Concept. The purpose of this experiment is to calculate an estimated value for the emissivity of bread at the moment it becomes toast. Emissivity is described as a coefficient that is used to define the ratio of heat transfer that an object receives from a given black body. In the following experiment, the heating device on the toaster is assumed to be a black body, or a body that absorbs all light energy transferred to it. The heating device cannot possibly be a black body, but it can be assumed as such for the purposes of this experiment.
The Method. The black body (toaster) transfers heat to the non-black body (the bread) at a rate defined by the emissivity of the bread. The relation between emissivity and rate of heat transfer is defined in Stefan-Boltzman’s law:
Q = AF (T14- T24)
Where:
Q = The max rate of transfer the black body can supply
= The Emissivity of the toast (non-black body)
A = The surface area of the bread being toasted
F = View factor, a ratio of the area of the heating surface to that of the surface being heated
= Stefan - Boltzman’s Constant
T1 = Temperature of heating element
T2 = Temperature of bread slice before being heated (room temperature)
Before utilizing this equation, however, it must be defined as to what actually constitutes toast. The emissivity of bread before being heated is a different value than the emissivity of a well-toasted piece of bread. A specific point of the heating process must then be chosen to find the emissivity at that given point. The goal is to find the emissivity at the exact point that bread becomes toast. That point, however, is subjective. No point can specifically be designated as the point at which bread becomes toast. In light of this subjectivity, the aforementioned point of toast must be assumed. This loop-hole of sorts only affects the Q value in Stefan - Boltzman’s law, however, all other values of the law (excluding emissivity) are either given or easily measured.
When Bread Becomes Toast. To discover the point at which bread becomes toast, a touch test of four slices of bread at different heated levels is implemented. Through the course of the test, it is agreed that a power setting of “4” on the toaster is the setting at which bread becomes toast. Unfortunately the mechanics of the power distribution at different settings on the toaster are unknown. The power rating displayed on the bottom of the toaster is that of 0.4 Kilowatts. Since it is unknown whether or not the 4th setting is a percentage of the total power or another function of the total power (i.e. time), 0.4 is assumed to be the power of the toaster. Outside of the experiment, lighter colored objects would require more power to heat to the same level as the toast and darker colored objects would not require as much as 0.4 Kilowatts, thus differentiating emissivities between objects.
Calculating Emissivity. To use the 0.4 Kilowatt measurement of power it must be converted into units that coincide with Stefan - Boltzman’s constant. Power units of Btu/hr (British Thermal Units per hour) are necessary. Temperature must also be in terms of the constant. Fortunately, both room temperature and the temperature of the heating element when energized are given in such terms. Area is easily measured in feet and the view factor is simply a ratio of this area to the are of the heating element. All values of Stefan-Boltzman’s law are then defined, with the exception of emissivity. Left with only one variable, emissivity is far from difficult to calculate.
Hahahahahaha hah haaaaaa.