Saturday 16 August 2014

Preparing for Lower Sixth Physics #16: Parallel lines

Here's a power line on northern Germany photographed on the way to Berlin. The very top wire is the earth wire but lower down there are 6 pairs of wires. Electric current travels in all 12 wires simultaneously. If you put two wires end to end, the calculations are simple: total resistance = resistance 1 + resistance 2.
It is more complicated to work out the total resistance if the wires run side by side. You can't just work out the total resistance. You have to calculate the RECIPROCAL of the total resistance which is written as 1/total resistance.
For two wires in parallel,
RECIPROCAL OF TOTAL RESISTANCE = RECEIPROCAL OF RESISTANCE 1 + RECIPROCAL OF RESISTANCE 2.

Or 1/total resistance = 1/resistance1 + 1/resistance2