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.
Nucleus, The “brains” of the cell, the nucleus directs cell activities and contains genetic material called chromosomes made of DNA.
Answer:
A higher frequency causes a shorter wavelength and higher energy.
A shorter frequency causes a greater wavelength and low energy.
Explanation:
Frequency is the number of waves that move at a period of time. It is measured by counting the number of crest point.
Wavelength is the distance between waves. A wave with higher frequency have crest that a very close and therefore the distance between them or wavelength is short compare to a wave with low frequency that the distance are farther apart and they have long wavelength. Therefore to generate high frequency of wave , more energy is required to do this .
The answer is D.) the process where distribution of molecules is balanced out by their movement.
Prokaryotes are chiefly defined as cells without a nucleus to contain the genetic information. Bacteria do not have a nucleus but, like prokaryotes, a nucleoid region in the center where the DNA can be found. Bacteria also do not have membrane-bound organelles, but they do have ribosomes to synthesize proteins. Bacteria vary a lot in the different structures they can have, but these basic factors make bacteria prokaryotes.
Hope this helps! :)
