Monthly Archives: January 2010

Measuring Radioactivity – The Geiger-Muller Tube

Radioactive emissions cause ionisation when electrons are chipped off atoms, rather like bullets chipping bits off stonework. The electrons are negatively charged, so if we could sweep them up with a + voltage and measure the current they generate, we … Continue reading

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Half Life

When nuclei decay, we can plot a graph to show how the number of undecayed nuclei changes with time. It’s very predictable, different for each isotope, but the graph is a very particular shape, called an exponential. Notice, the shapes … Continue reading

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Carbon dating

Carbon has several isotopes. Carbon 12 is the stable variety, radioactive Carbon 14 has a half life of just under 5800 years. Any living organism takes in both radioactive and non-radioactive carbon, either through the process of photosynthesis, or by … Continue reading

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Radioactivity – quick history

Henri Becquerel had already noticed that uranium bearing crystals in a locked drawer could darken wrapped photographic film and such ’emanations’ – as he called them –  could turn air into an electrical conductor, it seemed.  His crystals needed no energy … Continue reading

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Motors in Reverse

The opposite effect to the motor effect is that if a wire is moved in a magnetic field, a voltage (EMF) is produced across its ends, and if there is a complete loop, a current will flow in the loop.   In other words … Continue reading

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