Fuel cells can make an electricity from a simple electrochemical
reaction in which oxygen and hydrogen combine to form water. There are several
different types of fuel cell but they are all based around a central design
which consists of two electrodes, a negative anode and a positive cathode.
These are separated by a solid or liquid electrolyte that carries electrically
charged particles between the two electrodes. A catalyst, such as platinum, is
often used to speed up the reactions at the electrodes. Fuel cells are
classified according to the nature of the electrolyte. Every type needs
particular materials and fuels and is suitable for any applications. The
article below uses the proton exchange membrane fuel cell to illustrate the
science and technology behind the fuel cell concept but the characteristics and
applications of the other main designs are also discussed. Proton Exchange Membrane Fuel Cells (PEMFC)
The hydrogen ions permeate across the electrolyte to the
cathode, while the electrons flow through an external circuit and provide
power. Oxygen, in the form of air, is supplied to the cathode and this combines
with the electrons and the hydrogen ions to produce water. These reactions at
the electrodes are as follows:
Anode: 2H24H+ + 4e-
Cathode: O2 + 4H+ + 4e- 2H2O
Overall: 2H2 + O22H2O + energy
PEM cells operate at a temperature of around 80°C. At this
low temperature the electrochemical reactions would normally occur very slowly
so they are catalysed by a thin layer of platinum on each electrode.
Answer:
The answer is the tilt of the earth affects how directly the sun's rays hit different parts of the earth.
Answer:
The goal of materials engineering is to predict and control material properties through an understanding of atomic, molecular, crystalline, and microscopic structures of engineering materials
Answer:
Tigers are often poached for their parts, used in traditional __chinese_____ medicine.
Explanation:
Traditional Chinese medicine for over a thousand years has used the strength of the tiger to cure various physical and spiritual ailments. For this they need parts of the tiger such as their eyes, bones, teeth etc.
Below are some of the ailments treated:
-Tiger claws: It is used as a sedative for insomnia.
-Teeth: They are used to treat fever.
-Fat: It is used to treat leprosy and rheumatism.
The tiger is in danger of extinction, but they are still hunted to be used in medicine
<span>Earth went through a period of hot and also dry conditions and a wide spread drought.These conditions favored reptiles and therefore causing them to evolve during those conditions. Hope this helps :)</span>
