8/12/2019 Ces Edupack Answer on Coins

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Copper or not so copper coins?

Answer i):1) Open up the CES software and when prompted, select Level 2.There are three options: Browse; Select and Search, by default the Browse

option is selected.

2) By using the search option you can search for specific terms. Select thesearch option and type in bronze. A results list is generated and double-clickingon any material will produce its detailed description in the box on the right.Double-click on bronze to review its description and note down its price (given inGreat Britain Pound per kilogram i.e. GBP/kg).

Figure 1: Obtaining information for Bronze using the search facility.

3) Repeat step 2) but this time type in low carbon steel or mild steel. Select lowcarbon steel from the results list and note down its cost from the descriptiongiven.

The price of bronze is: 3.205 4.172 GBP /kg.

The price of mild steel is: 0.223 0.383 GBP /kg.

By converting the prices into pence per gram (p/g) gives:

bronze: 0.3205 0.4172 p/g;mild steel: 0.0223 0.0383 p/g.

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a) Material cost of bronze coins

1p coinMinimum cost = 3.56g x 0.3205 = 1.14p Maximum cost = 3.56 x 0.4172 =1.49p

So the cost of bronze used to make a 1p coin is 1.14 1.49p.

2p coinMinimum cost = 7.12g x 0.3205 = 2.28p Maximum cost = 7.12 x 0.4172 =2.97pSo the cost of bronze used to make a 2p coin is 2.28 2.97p.

b) Material cost of mild steel coins1p coinMinimum cost = 3.56g x 0.0223p = 0.08p Maximum cost = 3.56g x 0.0383

= 0.14pSo the cost of mild steel used to make a 1p coin is: 0.08 0.14p.

2p coinMinimum cost = 7.12g x 0.0223p = 0.16p Maximum cost = 7.12 x 0.0383 =0.27pSo the cost of mild steel used to make in a 2p coin is 0.16 0.27p.

Answer ii)Thus, using bronze for coinage purposes costs more than the actual face valueof the coin. By replacing bronze with a mild steel core, the costs are significantlyreduced and the material costs involved are much lower than the face value ofthe coins. It must be noted for the latter that as the coins are copper plated theoverall costs would be slightly increased to include further material costs (due tothe very thin layer of copper) and the extra processing costs.

Indeed copper-plated steel coins were introduced as a result of increasing metalprices on the world markets and hence as a cheaper alternative to bronze coins.The copper plating serves two main purposes: 1) it prevents the underlying steelfrom corrosion and 2) so that the coins appear aesthetically similar to theirpredecessors.

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Answer iii)Using CES (follow steps 1-3 given in answer part i) and note the density valuesfor bronze and mild steel from the respective descriptions given.

Density of bronze: 8500 9000 kgm-3

Density of mild steel: 7800 7900 kgm

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The density of steel is lower than bronze, hence to maintain a similar mass anddiameter of the coins, the copper plated coins are thicker than their bronzecounterparts.

The thicknesses1for:1p coins are: bronze = 1.52mm; copper-plated steel = 1.65mm2p coins are: bronze = 1.85mm; copper-plated steel = 2.03mm

Answer iv)Using a mild steel core means that coins since 1992 are magnetic, hence theeasiest way to distinguish between the pre-1992 and 1992- coins is by using amagnet.