A metal sphere initially has a charge of −9 nC-9\ \mathrm{nC}−9 nC. Electrons carrying 4 nC4\ \mathrm{nC}4 nC of negative charge leave it. A second sphere has a charge of +2 nC+2\ \mathrm{nC}+2 nC. Which statement describes the first sphere and the interaction between the spheres?
The first sphere has −13 nC-13\ \mathrm{nC}−13 nC and the spheres repel.
The first sphere has −5 nC-5\ \mathrm{nC}−5 nC and the spheres attract.
The first sphere has −13 nC-13\ \mathrm{nC}−13 nC and the spheres attract.
The first sphere has −5 nC-5\ \mathrm{nC}−5 nC and the spheres 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.