Name: Advantages and Disadvantages of Fossil Fuels
Uploaded: 2019-07-19
Duration: 5 min 44 s
Description: In this module, we will refresh our knowledge of fossil fuels. We will also learn about the various advantages and disadvantages of the excessive use of foss...

Question

Draw a labelled diagram of a solar cooker. What purpose are served by the blackened surface, glass cover plate and the mirror in a solar cooker? What would happen if the plane mirror of a solar cooker is replaced by a concave glass mirror?

Accepted Answer

Principle of working

Solar heating device (solar cooker or solar water heater) uses solar energy directly for heating purpose. Since solar energy falling on the earth is mostly very diffused, so it is concentrated and then collected. This can be done by using:

1. Black painted surface: Since a black surface absorbs more heat as compared to a white surface, so in designing solar heating devices, black painted surfaces are employed, so that they absorb the maximum amount of heat (infrared rays) from the sunlight falling on them. So the inner sides of solar heating devices are made black.

2. Glass sheet cover: Use of a glass sheet cover over the heating device, permits both visible and infrared parts of sunlight to pass through and go inside the solar device, which absorbs infrared rays, which in turn produces a heating effect. Consequently, when such a glass-covered heating device is kept in Sun for some time, its inner surface becomes very hot, which starts radiating heat in the form of infrared radiation. Since glass cover has a typical property, so it does not allow these absorbed radiations to escape out and therefore, retains the heat inside.

3. Reflector: increases the efficiency of the heating device by collecting more and more heat rays from the Sun. Generally, a plane mirror is employed as reflector. However, in solar devices in which very high temperatures are to be maintained, spherical reflectors (such as a concave reflector or parabolic reflector) are employed.

If a plane mirror is replaced by a concave glass mirror then the solar radiations will be focussed at a point. This will improve the efficiency of the solar heater.

Draw a labelled diagram of a solar cooker. What purpose are served by the blackened surface, glass cover plate and the mirror in a solar cooker? What would happen if the plane mirror of a solar cooker is replaced by a concave glass mirror?

Important Questions on Sources of Energy

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