AirbusA380
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Hey guys,
Im currently doing prelim 1/2 physics and doing pretty well overall (<90%). My question is, im really struggling condensing the info in the textbook down. Some of my notes for one section of the chapter can be up to 3 - 4 pages (2 sheets) long, and i struggle finding the most important, from the stuff that is relevant and helps my understanding that i should still remember from the stuff thats total rubbish. Any tips/advice?
Can someone provide a sample of this section condensed?
In a battery, or cell as we should say, the source of EMF is the chemical energy stored in the materials used. As we saw at the beginning of the last chapter, atoms have varying abilities to attract electrons—chemists call it electronegativity. A cell basically consists of two materials with different electronegativities, between which there is what we shall call a 'go-between' material.
The chemistry of electrical cells can be very complex, but for our purpose it is sufficient to realise that electrons will flow from the material of lower electronegativity (for example zinc) to the one of higher electronegativity (for example copper) through the external circuit connected to the terminals.
In the diagram material A has the highest tendency to attract electrons and material C the lowest. Material B acts as the 'go-between'. It is effectively a conducting material that allows the other two materials to 'trade' electrons by undergoing a chemical reaction with each of them which either replaces the electrons lost (material C) or takes up the electrons gained (material A). In the course of this process the positive and negative ions in material B migrate towards A and C respectively. As a result of these reactions, material B is eventually used up and the product of the reactions replaces it. At this stage the cell stops working and we say it has gone 'flat'.
The properties of the materials chosen for A, B and C are very important. Materials A and C must have as different electronegativities as possible but also undergo suitable reactions with material B. Material B must allow the migration of the ions (charged atoms) formed in the reaction and so is normally a liquid or a moist paste. In a dry cell, C is the outer zinc casing, and B is a paste of ammonium chloride and other special substances (see Figure 2.22). Material A is not actually a metal but manganese dioxide powder, which is mixed with the ammonium chloride paste. The carbon rod in the centre of the cell is there to collect the current. In a charged car battery, A is lead dioxide coated on a lead plate, B is a solution of sulfuric acid and C is a lead plate. As current from the car battery is used, lead from the lead plate is converted into lead sulfate, which remains as a coating on the plate. The lead dioxide is also converted into lead sulfate, which remains on the other plate. Fortunately this process can be reversed by forcing an electric current through the battery in the opposite direction, and so the battery can be recharged. This is one of the functions of the car's alternator.
There are many other types of cells in use. Some are single use and some (so-called 'Ni-Cads' for example) can be recharged. There is now considerable incentive for manufacturers to develop smaller, more efficient rechargeable batteries for use in electric cars and portable electronic devices.
Thanks.
Im currently doing prelim 1/2 physics and doing pretty well overall (<90%). My question is, im really struggling condensing the info in the textbook down. Some of my notes for one section of the chapter can be up to 3 - 4 pages (2 sheets) long, and i struggle finding the most important, from the stuff that is relevant and helps my understanding that i should still remember from the stuff thats total rubbish. Any tips/advice?
Can someone provide a sample of this section condensed?
In a battery, or cell as we should say, the source of EMF is the chemical energy stored in the materials used. As we saw at the beginning of the last chapter, atoms have varying abilities to attract electrons—chemists call it electronegativity. A cell basically consists of two materials with different electronegativities, between which there is what we shall call a 'go-between' material.
The chemistry of electrical cells can be very complex, but for our purpose it is sufficient to realise that electrons will flow from the material of lower electronegativity (for example zinc) to the one of higher electronegativity (for example copper) through the external circuit connected to the terminals.
In the diagram material A has the highest tendency to attract electrons and material C the lowest. Material B acts as the 'go-between'. It is effectively a conducting material that allows the other two materials to 'trade' electrons by undergoing a chemical reaction with each of them which either replaces the electrons lost (material C) or takes up the electrons gained (material A). In the course of this process the positive and negative ions in material B migrate towards A and C respectively. As a result of these reactions, material B is eventually used up and the product of the reactions replaces it. At this stage the cell stops working and we say it has gone 'flat'.
The properties of the materials chosen for A, B and C are very important. Materials A and C must have as different electronegativities as possible but also undergo suitable reactions with material B. Material B must allow the migration of the ions (charged atoms) formed in the reaction and so is normally a liquid or a moist paste. In a dry cell, C is the outer zinc casing, and B is a paste of ammonium chloride and other special substances (see Figure 2.22). Material A is not actually a metal but manganese dioxide powder, which is mixed with the ammonium chloride paste. The carbon rod in the centre of the cell is there to collect the current. In a charged car battery, A is lead dioxide coated on a lead plate, B is a solution of sulfuric acid and C is a lead plate. As current from the car battery is used, lead from the lead plate is converted into lead sulfate, which remains as a coating on the plate. The lead dioxide is also converted into lead sulfate, which remains on the other plate. Fortunately this process can be reversed by forcing an electric current through the battery in the opposite direction, and so the battery can be recharged. This is one of the functions of the car's alternator.
There are many other types of cells in use. Some are single use and some (so-called 'Ni-Cads' for example) can be recharged. There is now considerable incentive for manufacturers to develop smaller, more efficient rechargeable batteries for use in electric cars and portable electronic devices.
Thanks.
