Children could make a survey of the classroom, noting all the devices that use mains power and all those that use batteries. They could go on to research and write a set of rules for how to safely use mains-powered devices. They could also develop a trouble-shooting guide to using battery-powered items, after experimenting with how to arrange batteries to make something like a torch work. Develop this work further by challenging pupils to build simple switches using drawing pins and paperclips, like the ones shown briefly in the clip. Pupils could test their switches using simple components such as bulbs, buzzers, motors and batteries.