C: capacitance
εo: permittivity of free space (value: 8,85 x 10
-12 F.m
-1)
A: area of the plates
d: distance between the plates
Audio 1
(Since Area is given, we will use this new equation to calculate C. Change 5mm to 5m.)
The answer of 7,08 x 10-11F can be changed to pF.
How:
    7,08 x 10-11F
= 70,8 x 10-12 F
= 70,8 pF
(Remember that p = 10-12)
Audio 2
The Area is
0,4cm2.
To convert a cm2 to m2 you must:
• divide by 100, and divide by 100 again
Hence 0,4cm
2 = 4 x 10
-5m
2
Now substitute:
To convert the answer to mm, multiply by 1000.
    0,0177 x 1000
= 17,7mm
Audio 4
The Area must be maximised.

C is proportional to A, so an increase in A will result in an increase in C.
Audio 6.1
C is inversley proportional to d.
Hence the distance between the plates must be minimised.
Audio 6.2
C is proportional to the dielectric constant

Use a substance that has the highest possible dielectric constant.
Audio 6.3
Area = 3 x 12
      = 36cm
2
Then 36 ÷ 100 ÷ 100
      = 3,6 x 10
-3 m
2
Thus
Audio 7