An uncharged aluminum sphere is suspended from an insulating silk thread. A glass rod is rubbed with a silk cloth, causing the rod to become positively charged.
Explain, in terms of electrons, why aluminum is an electrical conductor but silk is an electrical insulator.
Describe how the positively charged glass rod may be used to induce a net negative charge on the suspended aluminum sphere.
The aluminum sphere is successfully given a net negative charge. Describe the direction and pattern of the electric field lines that surround this negatively charged sphere.
452 exam-style questions on CIE IGCSE Physics 4.2 Electrical quantities, covering 4.2.1a Positive and negative charge, 4.2.1b Charging by friction and detecting charge, 4.2.1c Electrical conductors and insulators, 4.2.1d Electric fields and electric field patterns, 4.2.2a Electric current, charge and measuring current, 4.2.2b Conduction in metals and the direction of current, 4.2.2c Direct current and alternating current, 4.2.3a Electromotive force, 4.2.3b Potential difference and voltmeters, 4.2.4a Resistance, 4.2.4b Resistance of a metallic wire, 4.2.4c Current–voltage graphs, and 4.2.5 Electrical energy and electrical power. Each one has a worked solution and a mark scheme showing where the marks go.