When building your own parabolic cooker it is important to build your pot stand at the focus.

Using the rectangular coordinate system allows us to draw a picture and determine mathematically where the focus is located .

Example 1 Graph:

Parabolic Solar Cookers      Page 4 of 5
How To Calculate the Focus
Example 1: A mirror is shaped like a parabaloid of revolution and will be used to concentrate the rays of the sun at its focus, creating a heat source. If the mirror is 20 feet across at it's edge and is 6 feet deep, where will the heat source be concentrated? Solution: We draw the parabola used to form the dish on a rectangular
coordinate system so that the vertex of the parabola is at the origin and its focus is on the positive y-axis.
The form of the equation of the parabola is and its focus is at (0, a).
Since (10, 6) is a point on the graph, the equation is:


The heat source will concentrate 4.17 feet from the center (vertex) of the dish, in a direct line of sight toward the sun.


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  A gimbaled pot support  made from 12" used  bicycle  rim attached to metal tubing.


Example 2 Graph Diagram:

Example 2: A satellite dish is shaped like a three-dimensional parabola. The signals that emanate from a satellite strike the surface of the dish and are reflected to a single point, where the receiver is located. (When sunlight strikes the mirrored surface of the dish, it will reflect to the same point. This is where the cooking pot should be located for solar cooking.) If the dish is 8 feet across at its origin and is 3 feet deep at its center, at what position should the receiver be placed?

Solution: We draw the parabola used to form the dish on a rectangular coordinate system so that the vertex of the parabola is at the origin and its focus is on the positive y-axis. The form of the equation of the parabola is and its focus is at (0, a).

Since (4, 3) is a point on the graph, the equation is:
The receiver should be located 1? feet from the center (vertex) of the dish, along a direct line of sight toward the sun.


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This lamp which lights our path fortells...the shape of things to come!


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The pot support on this 6' stainless steel dish is attached to a piece of tubing coming up through the center of the dish.
     Bart Orlando (blowing off steam)
Depressurizing the pressure cooker.
Brown rice cooked in 30  min in a pressure cooker a parabolic dish.
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