In: Physics
A regular icosahedron, as shown in the figure, has an outer
radius (defined as the distance from the centre to a vertex) of
9.51 cm and an inner radius (defined as the distance from the
centre to the centre of a face) of 7.56 cm. It has 20 faces which
are equilateral triangles with side length 10.0 cm, and 12
vertices.
Twelve negative charges of magnitude 20.0 μC are placed at the
vertices and 20 positive charges of magnitude 12.0 μC are placed at
the face centres. A positive charge of Q = +44.25 μC is placed at
the centre of the icosahedron.
What is the force acting on the charge at the centre of the icosahedron? [1]
If one of the negative charges at a vertex is removed, what is the force on the charge at the centre of the icosahedron? [2]
If one of the positive charges at the face is removed, what is the force on the charge at the centre of the icosahedron? [2]
Using your answers to parts ii) and iii) what is the net force on the charge Q at the centre if a complete face (i.e. one positive charge and the three surrounding negative charges), is removed? [5]