• Question: Dear scientist I have got three penny's and two of them are magnetic and the other isn't,why is that? Regards Oliver Benzing

    Asked by Anon to Cryogenic's Group on 13 Jul 2015.
    • Photo: RAL Cryogenics

      RAL Cryogenics answered on 13 Jul 2015:

      Hi Oliver,

      I wasn’t sure of the answer to your questions so I used the wonderful power of Google and learnt something new myself.

      Apparently originally pennies and two-pence pieces were made from copper, but only until 1860 (which is why some people refer to them as coppers). More recently they have been made from copper-plated bronze until 1992 and copper-plated steel since 1992. Steel is magnetic and bronze is not – you could check the dates on the coins you tested.

      According to Google, the only reason they changed what material the coins were made from was to reduce production costs – I guess there are a lot of pennies out there in the world, so saving a small amount on manufacturing cost of each coin will add up over the numbers of pennies they must make.

      Hope you enjoyed the rest of your day at Harwell!

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