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 term autotrophs refer to all plants because of their ability to undergo photosynthesis (the process of food preparation using light as a source)
winds also B. because winds change the air pressure meaning thats the answer
Answer: Im pretty sure the answer is C.) DNA -> gene -> chromosome -> nucleus
Explanation:
Answer:
In all different levels of the food webs and food chains, it is seen that damaged members of the prey have become easy food for the predators.
Explanation:
Preys can identify the other members of their species are injured or wounded or fed by the predators by their body fluid in as if a predator eats the prey the blood or other body fluid releases. These fluids or blood help individual prey species to be aware of the predator as they recognize that their species member is wounded or consumed by there olfactory receptors.
There are several other chemicals cue that is species specif that are released by the prey to alarm the other species member by injured or dead members.
Thus, the correct answer is - In all different levels of the food webs and food chains it is seen that damaged members of the prey have become easy food for the predators.
