PHYSICS - Energy - Energy Use in Electrical Appliances

Do you ever have arguments at home about leaving appliances on and wasting electricity? In this video we are going to look at measuring energy use, in electrical appliances. The unit of energy is the Joule (J). However, when dealing with electricity, we actually use Watts (W). A Watt is a measure of power where 1 Watt is equal to 1 Joule per second So a 100W light bulb uses 100J of energy every second An electrical device will have a power rating. This is the amount of electrical energy the device needs to work. We can calculate how much electrical energy a device transfers, by multiplying the power rating (W) by the amount of time the device is on for (in hours) The unit of electrical energy transferred is the Watt Hour (Wh). This is likely to be a very large number, so we usually give the number as kilowatt hours where 1kilowatt hour is equal to 1000 Watt hours. Let’s look at an example. A computer has a power rating of 250W. If it is used for 6 hours how much energy is transferred to it? Can you substitute the values into our equation? So how much would that cost to use? To work this out we have to know how much a kWh costs. This differs between different countries, different companies within a country, and even different tariffs from the same company. A whole office of computers… the price starts to clock up quite quickly. And that’s before we think about the lights, and charging our phones.