Fig. 112
"I have connected the ammeter so that it will indicate thousandths of an ampere, and you see that the needle moves only slightly. We cannot call it more than .001 ampere." Each boy in turn tried sending the current through his tongue and each tried to tell how it felt. One said it tingled, another said it felt warm, another said it tasted sour and the other said he did not feel or taste anything. "Well," I said, "whether you feel anything or not one-thousandth of an ampere is passing through your tongue and you are offering fifteen hundred ohms of resistance.
(1.5 volts)/(1500 ohms) = .001 ampere
"Your hand offers nearly seventy times as much resistance as your tongue. Suppose we try increasing the voltage, or pressure, of our electric current. We will connect in series the ten cells, making a battery which you see by the volt meter gives fifteen volts of pressure. We now find that having ten times the pressure it sends ten times as much current as formerly through the tongue."
(15 volts)/(1500 ohms) = .01 ampere
Each one now testified that the battery sent all the current he cared to take through his tongue. If they send one thousand times as much as that through a criminal no wonder it kills him. It produces a twitch when the contact is first made, afterward a decided sensation of warmth and acid taste.
If we should increase the voltage tenfold more, say the 110-volt dynamo current (direct current), and touch the bare conductors with our hands, the ammeter would indicate about .001 ampere. That is, although this current has about seventy times as much push, or voltage, as a dry cell, no more electricity passes through the fingers than did through the tongue in the preceding experiment with one cell. The fingers offer so much greater resistance.