Excel - why use a logarithmic scale in a chart?

[Polly]

I understand how to change the scale on the value axis to logarithmic, I am
just not sure why I would do so.

 

[Luke M]

Usually helpful when:
a) Trying to plot exponential series (such as in calculus, some physics,
etc)
b) Trying to distort data so your customers don't see how badly your company
is losing money *grin*

 

[David Biddulph]

If in your chart you have some large numbers and use a linear scale, you
won't see differences in small numbers.
try, for example a series like
1
2
1.00E+05
2.00E+05
Plot the series on a linear scale (& see whether you can see the difference
between the first two points), then change it to log.