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Complex Number z has modulus 1
Complex Number u
Describe the use of electrostatic charging in an electrostatic precipitator.
An electrostatic precipitator (ESP) is a device that removes particulate matter from exhaust gases using electrostatic forces. It is commonly used in industries such as power plants, cement factories and steel mills to control air pollution.
The basic principle of an ESP is to use an electric field to charge the solid particles in the gas stream, and then collect them on a charged surface.
1. The gas stream is first passed through a series of electrodes, which are typically made of metal wires or plates. These electrodes are charged with a high voltage, usually in the range of tens of thousands of volts.
2. As the gas stream passes through the electrodes, the solid particles in the gas become charged, either positively or negatively depending on the polarity of the electrodes. The charged particles are then attracted to an oppositely charged collection electrode, which is usually a flat metal plate or a series of plates.
3. As the particles collect on the collection electrode, they form a layer of solid deposits that can be removed periodically. This is done by rapping on the collection plates, which causes the solid deposits to fall into a hopper or other collection device.
How can energy be transferred from one energy store to another?
Energy can be transferred from one store to another:
i) Mechanically (by a force acting over a distance)
Eg: a car moving up an inclined plane
(chemical potential energy –> gravitational potential energy)
ii) Electrically (by an electric current)
Eg: lighting up a bulb in an electric circuit
(chemical potential energy of battery –> light and heat energy of light bulb)
iii) By heating (due to a temperature difference)
Eg: a gas stove heating up a pot of water
(chemical potential energy of gas –> internal energy of water)
iv) By propagation of waves (both electromagnetic and mechanical)
Eg: a dipper producing surface water waves
(mechanical energy of dipper –> kinetic energy of water waves)
What is an energy store?
An energy store is a substance or a physical system that can store energy in various forms.
Some examples of energy stores are:
– batteries (chemical potential energy)
– a stretched spring (elastic potential energy)
– fuels (chemical potential energy)
– a dammed water body (gravitational potential energy)
– tidal waves (kinetic energy)
– radioactive isotopes (nuclear energy)
Describe depolymerisation as a process in which polymers are broken down into their monomers, exemplified by hydrolysis of polyesters using acid as a catalyst.
Depolymerisation is a process which involves breaking down the plastic polymer into its monomer units. The monomers can then be purified and used to create new plastics.
An example is the hydrolysis of polyesters using acid as a catalyst.
In the hydrolysis process, the ester linkages that hold the polymer chains together are broken. The polyesters will be broken down to form a large number of dicarboxylic acid monomers and diol monomers.
Conditions for hydrolysis of polyesters:
– An acid catalyst, usually sulfuric acid or hydrochloric acid
– Water as a reactant
– High temperature of between 80 deg C to 150 deg C
Describe the potential effects of the increased levels of greenhouse gases like carbon dioxide and methane.
Increased greenhouse gas concentrations trap more heat in the Earth’s atmosphere, causing the average temperature on Earth to increase. This phenomenon is known as global warming. Global warming can result in more extreme weather events and the melting of polar ice.
1. Melting of ice caps and glaciers
The rising temperatures can cause ice caps and glaciers to melt, resulting in rising sea levels and increased flooding in low-lying coastal regions.
2. Extreme weather events
The rising temperatures can cause changes in precipitation patterns, resulting in more intense and frequent rainfall in some regions and more frequent and severe droughts in other regions. There will be more frequent and intense heat waves, droughts and extreme weather events like hurricanes and floods.
ABCD Four Points on a Circle
What are greenhouse gases? What are the sources of these greenhouse gases?
Greenhouse gases are gases that trap heat in the Earth’s atmosphere. Examples of greenhouse gases are carbon dioxide and methane. Too much of these greenhouse gases can result in global warming.
The sources of these gases:
1. Carbon dioxide
Carbon dioxide is released to the atmosphere mainly through the combustion of carbon-containing fuels, and the respiration of living organisms.
2. Methane
Methane is released to the atmosphere mainly through the decomposition of organic matter and from flatulence from livestock like cows, goats.