The document discusses how cross-sectional area is calculated using the formula A = πR^2, where A is the area, π is a constant equal to 3.14, and R is the radius. It provides examples showing that if the diameter is doubled from 300mm to 500mm, the radius increases from 150mm to 250mm. By doubling the diameter, the cross-sectional area increases by a factor of 4, since area is proportional to the square of the radius. So doubling the radius causes the area to be multiplied by 4.

1. Applied Electricity Two
Cross sectional area is calculated by using the formula:
∏R 2
∏ Pi is a constant = 3.14
R is the radius and it is squared
which means multiplied by itself
The Radius is half of the diameter

2. Applied Electricity Two
If you increase the diameter you increase the radius.
If the diameter is 300 mm the radius is 150 mm
If the diameter is increased to 500 mm
the radius is 250 mm

3. Applied Electricity Two
If you doubled the diameter of the conductor
you would change the cross sectional area
by how much?

4. Applied Electricity Two
Example:
A = ∏R2
=3.14 (150x 150)
=70685 mm 2
or
70685 x 10-6m2
or
70.685 x 10-3m 2

5. Applied Electricity Two
Example:
A= ∏R 2
=3.14 (300x 300)
=282,743 mm 2
or
282743 x 10-6m 2
or
.282743 m 2

6. Applied Electricity Two
After doubling the diameter we have an area of
282743
before the area was
70685
divide 282743 by 70685
=4
the area has increased by 4

7. Applied Electricity Two
By doubling the diameter (or radius) we have increased
the area
by 4.
If we had increased the diameter (or radius) by 3
we would increase the area by 9.
The increase is multiplied by itself because of the square
in the equation.

8. Applied Electricity Two
A is measured in m2 ( meters squared)
So if we are given a cross sectional area in mm2
we need to take into account that in the equation it will
need to be converted to m2 (meters squared)
2.5 mm2
in the equation looks like
2.5 x 10-6