A radial electric field distribution in free space is given in spherical coordinates as:

= o 3 o ( ≤ ) = (2 3 − 3 )o 3o 2 ( ≤ ≤ ) = (2 3 − 3 )o 3o 2 ( ≥ )

Where, rhoo, a, and b are constants. (a) Determine the volume charge density in the entire region (0 ≤ r ≤[infinity]) by the appropriate use of ∇ .D = . (b) In terms of given parameters, find the total charge, Q, within a sphere of radius r where r > b.

Determine the time of the day and month of the year at which the peak sensible cooling load occurs for a top floor, north-eastern corner room of an office building in durban for the following conditions: floor area: 8 x 8 x 3 m east and north walls: 115 mm face brick (outside), 20 mm air space, 115 mm ordinary brick (inside) with 15 mm plaster roof construction: suspended plasterboard ceiling, 450 mm air space, 150 mm concrete, 75mm screed, waterproofing no heat transfer across other surfaces window area 3x 1,5 m high in north wall only. ordinary glass with venetian blinds. lights and occupants : from 07: 00 to 18: 00 average light density: 25 w/m2 number of occupants : 5 seated, light office work room temperature 24°c