Q2. a) a) b) By sketching energy band diagrams, explain the differences in electrical properties of insulators (e.g. diamond) and metals (e.g. aluminium). Aluminium (Al) has a mass density of 2700 kg/m³. Estimate the density of conduction band electrons, stating the approximations you make. c) A flat, thin aluminium plate has an area 12 mm x 12 mm and acquires a charge of -25 pC. It is then electrically isolated and placed in a vacuum. (i) Calculate the number of electrons that must have been transferred during the charging process. (ii) Sketch the electric field distribution and equipotential surfaces outside of the plate, also showing how the charges distribute on the plate's surface. (iii) By first calculating the surface charge density, estimate the electric field magnitude just outside the mid-point of the plate.

Q2. a) a) b) By sketching energy band diagrams, explain the differences in electrical properties of insulators (e.g. diamond) and metals (e.g. aluminium). Aluminium (Al) has a mass density of 2700 kg/m³. Estimate the density of conduction band electrons, stating the approximations you make. c) A flat, thin aluminium plate has an area 12 mm x 12 mm and acquires a charge of -25 pC. It is then electrically isolated and placed in a vacuum. (i) Calculate the number of electrons that must have been transferred during the charging process. (ii) Sketch the electric field distribution and equipotential surfaces outside of the plate, also showing how the charges distribute on the plate's surface. (iii) By first calculating the surface charge density, estimate the electric field magnitude just outside the mid-point of the plate.