Year 10 have drawn field lines with plotting compasses and know the field is strongest near the poles, but they have never seen a number for it. The teacher lays a phone running phyphox's magnetometer flat on the bench and opens phyphox's remote access in the board's browser over the school wifi, having checked beforehand that the network lets the two devices connect, so the live graph fills the screen. With the magnet across the room, the trace sits at about 50 microtesla, which is Earth's own field, and the class notes that first. The teacher then slides a bar magnet towards the phone along a metre rule, pausing every 5 cm and stopping at 5 cm so the sensor is not overloaded, then repeats the approach with the magnet turned round so the other pole leads. Students record the reading at each distance in their books, sketch how quickly the field falls away, and write two sentences on what the reversed trace says about the two poles.
This page is one of a growing set of PICRAT examples by cell, subject and grade. Page maintained by Andy Perryer.