Two separate metal spheres P and Q are far apart on insulating stands. P has a charge of −8 nC-8\ \mathrm{nC}−8 nC and Q has a charge of +3 nC+3\ \mathrm{nC}+3 nC. Each is fully discharged to Earth. What is the overall effect on Earth?
Earth loses electrons carrying a net charge of −11 nC-11\ \mathrm{nC}−11 nC.
Earth gains electrons carrying a net charge of −11 nC-11\ \mathrm{nC}−11 nC.
Earth gains electrons carrying a net charge of −5 nC-5\ \mathrm{nC}−5 nC.
Earth loses electrons carrying a net charge of −5 nC-5\ \mathrm{nC}−5 nC.
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.