In a printing machine, a charged metal roller is mounted on insulating supports. The roller is brought close to a neutral metal guide plate, which also stands on insulating supports, without touching it. Electrons in the guide plate move towards the side nearest the roller. The roller is then connected to Earth by a copper wire until it is neutral. Which statement describes the initial charge on the roller and the flow of electrons in the copper wire?
The roller was positive; electrons flowed from the roller to Earth.
The roller was negative; electrons flowed from the roller to Earth.
The roller was negative; electrons flowed from Earth to the roller.
The roller was positive; electrons flowed from Earth to the roller.
91 exam-style questions on Edexcel GCSE Physics 11.1 Charging by friction, covering 11.1.1 Charging insulators by friction, 11.1.2 Forces between charges, 11.1.3 Electrostatic phenomena, and 11.1.4 Earthing and removing charge. Each one has a worked solution and a mark scheme showing where the marks go.