Just because AA batteries don’t have a high voltage output, don’t think that
they can’t hurt you. If you short them out, all the electrons will flow quickly
from the negative to the positive poles and generate a lot of heat — enough
heat, in some cases, to destroy the battery and possibly burn you. If you feel
heat coming from your circuit or the batteries, you might have a short-circuit
or a component inserted the wrong way. Turn it off and let things cool down;
then check to see what’s causing the problem.The resistance in your body can vary greatly. For example, if you have sweaty
hands and touch a live wire with one hand while the other hand rests on a
metal table, this is a very dangerous situation. Because you have moisture on
your hands — which lowers your contact resistance — a higher current will
flow through your body for a given voltage. If you have dry hands — one
hand touching a live wire, the other hand in your pocket — and your feet on
a dry, rubber mat, there’s far less danger from the same amount of voltage
because your resistance is higher. However, if a higher voltage comes your
way, even with the higher resistance, you could die. Bottom line: There is no
iron clad rule as to what level of voltage will kill or seriously injure a person
because of all the variables.Regardless of how much voltage you work with, develop safe work habits now.Chapter 2: Safety First......................................................................................................
Is it the voltage or the current — or both?
Electricityis the movement of electrons (cur-
rent)through a conductor when a voltage is
applied across the conductor. Electric current is
what burns your skin, stops your muscles cold,
and causes your heart to go into fibrillation. If
you touch a livewire (that is, any conductor at
some voltage), current can flow through your
body because it is a conductor. The amount of
current that flows through your body depends
upon your body’s resistance to the flow of elec-
tric current and how much voltage is applied.
Ohm’s Law deals with the relationship between
voltage, current, and resistance. Here’s the law,
for those among you who appreciate equations:
Current = Voltage ÷ Resistance
The calculation for what’s dangerous involves
the current, the voltage, and your body’s resis-
tance. The current passing through your body is
equal to the difference in the voltage that’s
being applied to two spots on your body (for
example, your hand touching an electric cir-
cuit and your feet touching the floor, or one hand
touching a live conductor and another hand rest-
ing on a chair), divided by your body’s resistance.