Over the last few centuries our exposure to electricity has increased by a phenomenal amount. Our houses are increasingly filled with gadgetry, time saving devices, lighting, TVs and stereos. At work a large proportion of people spend the majority of their day on a computer and surrounded by electrical machines. All these electrical appliances give off electrical fields. The electricity rays out from the appliance in what is called a "field". Electromagnetic fields are always vibrating; they always spread out into space indefinitely and carry alternating electric and magnetic vibrations.