Page 35 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

16 Chapter Three

The reason for this inconsistency is that the existence of electricity was
discovered long before it was fully understood. Electricity as a phenomenon was
known for quite some time, but it wasn’t until the early part of the 20th century
that George Thomson proved the existence of the electron at the University of
Aberdeen, Scotland. The men who established the original electrical theories
had to make decisions about things they didn’t fully understand. The direction
of current flow is one such example; for a variety of reasons, it was originally
believed that current flowed from positive to negative. As you may imagine,
this inconsistency can, and does, cause endless problems.

Capacitance
Now imagine a full water tank A connected by a blocked pipe to an empty
water tank 6 (Figure 3-6a). Assume that the contents of tank A are magically
maintained at the same level regardless of the amount of water that is removed.
At some time To (“time zero”), the pipe is unblocked and tank 6 starts to fill.
By the time we’ll call TFuLL, tank 6 will have reached the same level as tank A
(Figure 3-6b).
The speed with which tank 6 fills depends on the rate with which water
flows between the two tanks. The rate of water flow depends on the difference
in pressure between the two ends of the pipe and any resistance to the flow

A 6 A 0

w_

3 Em
c
m 7;

(a) Pipe linking tanks i5 blocked. (b) By time T,,,, tank B ha5 filled
Blockage i5 removed at time To to the same level a5 tank A.

Figure 3-6. Water tank representation of capacitance