A laboratory technician tests a charged plastic film whose type of charge is unknown. An initially neutral aluminium cylinder on an insulating surface rolls towards the film. After touching the film, the cylinder rolls away. Measurements show that electrons moved from the cylinder to the film during contact. Which explanation describes the film's initial charge and both movements of the cylinder?
The film is positive. Electrons shift to the cylinder's near side, causing attraction; the cylinder then loses electrons and becomes positive, so the two objects repel.
The film is negative. Electrons shift to the cylinder's far side, causing attraction; the cylinder then loses electrons and becomes positive, so the two objects repel.
The film is negative. Electrons shift to the cylinder's near side, causing attraction; the cylinder then gains electrons and becomes negative, so the two objects repel.
The film is positive. Electrons shift to the cylinder's far side, causing attraction; the cylinder then loses electrons and becomes positive, so the two objects repel.
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.