electrical wiring at home – the ring circuit

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Wikipedia has a good description of how a ring circuit is used in home wiring.  The diagram below is neater than the one I drew on my board in class.  You can click on it to view a larger version of the drawing.

drawing by Andrew C.
  • The ring circuit for power sockets is rated at 30A.
  • The ring design allows electricity to reach the socket from two different directions, so the current flowing in any one wire is lower.
  • Since the current is lower, a thinner cable can be used.  This saves money as copper is expensive.

Click below to download the Scout guide to home wiring.

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Using excel for AH Physics investigation graphs

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We spent some time today looking at ways of analysing data obtained from your investigation experiments. It is often a good idea to generate a graph of your results.  Your graph does not have to be drawn by hand, it can be produced on a spreadsheet.  If you do decide to use a spreadsheet, remember to print the gridlines on your final version of the graph.

If you use Excel, there is a function called linest that can be used to determine the gradient of the best-fit line and the intercept with the y-axis.  If you follow the instructions below, the linest function will also calculate the uncertainty in the gradient and intercept point for you.

Here is a linest tutorial to get you started.  It also includes instructions on how to add custom error bars to your graph.

Excel Tutorial: Using LINEST function, Plotting a graph, Adding Error Bars

I have included a pdf of a different help sheet – download it using the link at the end of this post.

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uncertainties booklet

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It’s time to start looking at the uncertainties in your investigation results.  I have attached a pdf of a guide to uncertainties in AH Physics.  You should pay particular attention to the sections on combining uncertainties and analysing graphs.

I will post additional resources to help you deal with uncertainties in your graph.

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