In Year 4 the introduction to electric circuits can be experimental and fun. I like to start by making a simple torch with an LED and a flat button type battery. This creates the idea of a circuit, so to progress from there I give out a whole range of switches that all work differently and a range of outputs, LEDs, buzzers, lights, and the students put them together in circuits to make them work. They record their findings. Once they understand the principles they can think about designing an alarm.