Video: How we measure electricity

Hello again, I’m Doctor Bruce Warrington, Australia’s Chief Metrologist.

Today I want to talk to you about how we measure electricity.

The basic electrical unit in our international system is the ampere, the unit of current or how much charge is flowing each second. It’s closely connected to the volt, for voltage, and the ohm, for resistance, because these three physical quantities are related through a famous equation called Ohm’s Law. All three units are named after scientists who helped develop our understanding of electricity.

Today our best electrical standards are quantum standards. It turns out that under just the right conditions, voltage and resistance are quantised – they have a kind of ruler of fixed steps, where the step size is set by fundamental constants and is always the same.

We can scale these measurements up and down to go from billionths of a volt - to millions of volts! This facility at the National Measurement Institute makes lightning to test parts of our electricity supply grid to make sure they are safe.

I think it’s fascinating that the electricity we use every day is ultimately measured using the quantum properties of nature – and I hope you don’t find that too shocking!