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.
The selection of more effective which is against recessive alleles in haploid organisms than diploid organisms. This is because haploid organisms contain a single set of alleles if a deleterious allele is present in haploid organisms which will produce its effect immediately as there will be no dominant allele which can prevent the expression of the recessive allele as it happens in diploids. Recessive allele will not produce its effect in presence of the dominant allele in the case of heterozygote which is Aa.
Where there is haploid the selection will be more effective when removing recessive alleles in the population. It is the homozygous recessive condition which as aa then the selection will act against recessive alleles.
<span>Maggie's training regimen may put her at risk to develop secondary amenorrhea. While amenorrhea is the absence of menstruation, secondary amenorrhea is the absence of the menstrual cycle in females who have started menstruating (having had at least one cycle) and then stop menstruating for a period longer than three months. Secondary amenorrhea occurs in times of extreme stress or weight loss (such as anorexia). Female soldiers have experienced secondary amenorrhea when they have gone to war or have become prisoners of war. Hormone shots, extreme weight gain, birth control, and certain medications also cause the condition.</span>
Hi :D
Neutrons are neutral so they have no charge. Electrons have a negative charge and protons have a positive charge.
For an atom's charge to be neutral there has to be an even amount of protons and electrons in the atom.
Answer:
Therefore, an isolated ecosystem, will only be sustainable if it fulfills the condition of Organizational Sustainability:
Explanation:
