http://www.bbc.co.uk/education/guides/zjjsgk7/revision/3
Source: http://www.bbc.co.uk/education/guides/zjjsgk7/revision/3
Short video covering calculations for energy used and cost for AQA GCSE Physics P1 3.3
Source: Mr R Pepperell: http://www.knowmia.com/watch/lesson/21444