To really understand what is happening in an electrical circuit,
we have to appreciate that something is actually moving in the
wires, and be able to imagine it. The direction of the current is
an important part of the mental model. Two circumstances help hide
this from us:
the easiest thing to study is a light bulb, which doesn't care
about the direction of current at all;
household electricity is alternating current, which changes
direction so fast that the current seems to be going both ways at
once.
The one place where current direction makes a difference in
everyday life is when we put batteries into something. If you put a
battery in backwards, the device most likely will not work.
This situation is rather common; in this section we meet the buzzer,
which cares strongly about which way the current is going.
Appliance plugs frequently are designed so that they can only go
into the receptacle one way. Is this also an example of the
direction of current? No, it turns out to be a safety feature.