17.47 How can birds sit on high voltage electrical cables and not be electrocuted?

Before you read this, I suggest you read posts 17.44 and 17.45 You often see birds perched on cables that are carrying electricity but aren’t insulated. In the UK electricity can be sent through overhead cables at 400 kV. Why aren’t the birds electrocuted? As charge moves along the cable, the voltage drops. Why? Because… Continue reading 17.47 How can birds sit on high voltage electrical cables and not be electrocuted?

17.46 Peeing contests: helping girls to study science

If you’re not a native English speaker, you may find it difficult to understand the title of this post. Peeing is a more polite way of saying the impolite word “pissing”; the words you will find in a dictionary are “urination” and “micturition”. What has this got to do with helping girls study science? I… Continue reading 17.46 Peeing contests: helping girls to study science

17.45 Electrical energy

Before you read this post, I suggest you read post 17.44. To move charge from a point with a low potential to a point with a high potential, we need to do work. This is the same as saying that moving a charge from a point with a low potential to a point with a… Continue reading 17.45 Electrical energy

17.44 Amps, volts and ohms

Before you read this post, I suggest that you read posts 16.25 and 17.17. Everybody knows that amps and volts are electrical units. But what, exactly, do we use them to measure? And, how are they connected by Ohm’s law? In post 16.25, we saw that amps (A) are used to measure electrical current. To… Continue reading 17.44 Amps, volts and ohms

17.43 Walking on water – surface tension

The insect in the picture is walking on water. You can see that it isn’t simply floating. To float, part of it would have to be submerged so that the upward force that previously acted on the displaced water balanced the downward force (weight) exerted by gravity on the insect (post 17.6). Instead, it is… Continue reading 17.43 Walking on water – surface tension