Q3. A) (i) Explain the physics behind the greenhouse effect and how it operates
ID: 1520189 • Letter: Q
Question
Q3. A) (i) Explain the physics behind the greenhouse effect and how it operates in the Earth's atmosphere (2 marks) (ii)What is the difference between a greenhouse gas and a CFC? (1 mark) B) The energy output per gram of a car battery is about 125 J and costs about 14 cent per kWh. The same weight of petrol gives out about 40,000 J and 1 kg costs approximately 150 cent. Use these numbers (and any other you feel are relevant) to compare the energy cost of electrical vehicles over petrol driven ones. (2 marks) C) Give two ways in which electrically driven vehicles have a negative impact on the environment and two ways in which they have a positive effect on the environment. (2 marks) D) In your own opinion, but based on the physics you have learned so far, is global warming real or not? Present the physics that supports your case.
Explanation / Answer
The greenhouse effect refers to circumstances where the short wavelengths ofvisible light from the sun pass through a transparent medium and are absorbed, but the longer wavelengths of the infrared re-radiation from theheated objects are unable to pass through that medium. The trapping of the long wavelength radiation leads to more heating and a higher resultant temperature. Besides the heating of an automobile by sunlight through the windshield and the namesake example of heating the greenhouse by sunlight passing through sealed, transparent windows, the greenhouse effect has been widely used to describe the trapping of excess heat by the rising concentration of carbon dioxide in the atmosphere. The carbon dioxide strongly absorbs infrared and does not allow as much of it to escape into space.
A major part of the efficiency of the heating of an actual greenhouse is the trapping of the air so that the energy is not lost by convection. Keeping the hot air from escaping out the top is part of the practical "greenhouse effect", but it is common usage to refer to the infrared trapping as the "greenhouse effect" in atmospheric applications where the air trapping is not applicable.
ii) A Greenhouse Gas is any gas which traps 'heat' on the earth, such as Carbon Dioxide (CO2) and Water Vapour (H20). CFCs (Chloroflurocarbons) are also greenhouse gasses, and are in fact very efficient greenhouse gasses. The have the added effect of breaking down ozone, which depletes the ozone layer allowing more ultraviolet light down to the surface, which isn't good. Also, they last for a long time - so any CFCs released now will stay in the atmosphere for a long time.
B) 1kWh = 1000*3600 J = 3600 kJ
3600 kJ by battery costs 14 cent
1 kJ by battery cost 14/3600 cent = 0.00389 cent
40000 kJ by petrol cost 150 cent
1 kJ by petrol cost 150/40000=0.00375 cent
petrol cost lesser.
C)
Two ways in which they have a positive effect on the environment:
Emissions: Electric cars are 100 percent eco-friendly as they run on electrically powered engines. It does not emit toxic gases or smoke in the environment as it runs on clean energy source. They are even better than hybrid cars as hybrids running on gas produce emissions. You’ll be contributing to a healthy and green climate.
Safe to Drive: Electric cars undergo same fitness and testing procedures test as other fuel powered cars. In case an accident occurs, one can expect airbags to open up and electricity supply to cut from battery. This can prevent you and other passengers in the car from serious injuries.
Two ways in which electrically driven vehicles have a negative impact on the environment:
1. Silence as Disadvantage: Silence can be a bit disadvantage as people like to hear noise if they are coming from behind them. An electric car is however silent and can lead to accidents in some cases.
2. Electricity isn’t Free: Electric cars can also be a hassle on your energy bill if you’re not considering the options carefully. If you haven’t done your research into the electric car you want to purchase, then you may be making an unwise investment. Sometimes electric cars require a huge charge in order to function properly – which may reflect poorly on your electricity bill each month.
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