A cloth has no overall charge. It is used to rub two identical rods, one after the other.
After rubbing, each rod has a charge of −3.0 μC-3.0\ \mu\text{C}−3.0 μC.
What is the charge on the cloth, and why?
+6.0 μC+6.0\ \mu\text{C}+6.0 μC, because it lost electrons to the rods
+3.0 μC+3.0\ \mu\text{C}+3.0 μC, because it lost electrons to the rods
−6.0 μC-6.0\ \mu\text{C}−6.0 μC, because it gained electrons from the rods
+6.0 μC+6.0\ \mu\text{C}+6.0 μC, because it gained protons from the rods
43 exam-style questions on OCR GCSE Physics 3.1 Static and charge, covering 3.1.1 Positive and negative charge, 3.1.2 Static electricity and forces between charged objects, 3.1.3 Electron transfer and static electricity, 3.1.4 Electric fields, 3.1.5 Current as a flow of charge, 3.1.6 Current in a single closed loop, and 3.1.7 Charge, current and time. Each one has a worked solution and a mark scheme showing where the marks go.