Question

a) What is a solar cooker?
b) Why is the inner surface of a solar cooker blackened?
c) What is the function of glass sheet that covers the box in a solar cooker?

Answer 1

(a) A solar cooker:

1. A solar cooker is a device that uses the energy of direct sunlight to heat, cook or pasteurize drinks and other food materials.
2. Many solar cookers currently in use are relatively inexpensive, low-tech devices, although some are as powerful or as expensive as traditional stoves, and advanced, large-scale solar cookers can cook for hundreds of people.
3. Since, they use no fuel and cost nothing to operate, many nonprofit organizations are promoting their use worldwide to help reduce fuel costs and air pollution and to help slow down deforestation and desertification.

(b) Reason for making the inner surface of a solar cooker blackened

1. Black surfaces are excellent absorbers of radiation and help in trapping more heat inside a solar cooker, hence improving the efficiency.
2. The function of the glass sheet in a solar cooker is to trap heat inside and thus, help to raise the temperature inside the cooker to a sufficiently high degree to cook the food.
3. When the sunlight hits the substance, it makes the molecules of the substance vibrate, and eventually, heat is developed.
4. Now, to run this process smoothly, a plane mirror and a glass sheet are used.

(c) The functions of the glass sheet that covers the box in a solar cooker

1. The function of the glass sheet in a solar cooker is to trap heat inside and thus, help to raise the temperature inside the cooker to a sufficiently high degree to cook the food.
2. So, what we do is concentrate the light coming from the sun in the direction where the cooking substance is placed. It is known as the cooking space.
3. To achieve this, plane mirrors are used to concentrate the sunlight. Sufficient amounts can be concentrated by reflecting sunlight on a plane mirror.
4. Now, the heat generated might escape into the atmosphere. To overcome this problem, a glass sheet is used in a solar cooker.
5. A glass sheet is used as a lid. It reduces the process of convection so that the heat does not escape from the inside air to the outside air.
6. The glass helps in absorbing the light and thus increasing the heat holding capacity of the solar cooker.