Question

(a) State the units of electric potential and electric potential energy. Sketch an equipotential surface at a distance r from a point charge q and state the magnitude of the work done in moving a small test charge along that surface. [5 marks] (b) The figure below shows four representations (labelled A, B, C and D, respectively), of the electric field lines between the plates of a parallel plate capacitor. Identify which drawing is correct and indicate what is incorrect in each of the other drawings. [6 marks] (c) A square parallel plate capacitor (with length of side -x) and a circular parallel plate capacitor (diameter-x), both with plate separation d, are filled with the same dielectric material (dielectric constant- 3.8). State which plate has the largest capacitance and explain your answer. Determine the dielectric constant needed in the circular capacitor to make its capacitance the same as that of the square capacitor. [5 marks] (d) If the square capacitor in (c) has a plate separation of 3 mm, and a plate length of 2 cm, calculate the charge stored on the plates for a potential difference of 1.9 kV Determine the energy stored in this capacitor. [4 marksl

Answer 1

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