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Why won't a standard 1.5V (or 1.2V) battery give an electric shock when touching both ends (positive and negative) in the same time? Even if the battery is capable to provide a short-circuit current of 1-2 amps. It is only because of the human body resistance?

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You skin resistance will ensure that you get nowhere near 1-2 A. However your skin resistance is from your skin; if you have an open cut it will be much less and you can be harmed much more easily.

Try putting a 9 V battery to your tongue if you wish to feel electricity safely. E&0

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  • \$\begingroup\$ No need to feel electricity :) I have done that when I was a kid :). I am just trying to understand if there are other reasons for not getting a shock beside the internal resistance of the battery and the resistance of the human body (skin). \$\endgroup\$ – Buzai Andras May 14 '12 at 20:17
  • \$\begingroup\$ The resistance of the human body is in the order of kiloohms while the internal resistence of a battery that delivers 1.2A at 1.2V when short circuited is order of magnitude smaller. Just to note... \$\endgroup\$ – Vorac Jul 6 '12 at 8:16
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The current a voltage source (like a battery in this case) delivers is up to the load. The current rating is only the maximum the source can deliver. It can't somehow force this onto the load. For example, if you connect a 1.5 kΩ resistor accross the 1.5 V battery, only 1 mA will flow. This will be true whether the battery or power supply was rated for 1 A, 10 A, or 100 mA, since all those are more than the 1 mA the load will draw.

What causes harm to your body and what you feel is current, not voltage. The published levels of how much current is safe vary quite a bit out there depending on what part of the body and what point the author is trying to make. You want to be extra careful running current accross the heart and thru the brain. Between two fingers of the same hand is relavtively safe in that it will be uncomfortable before you get hurt. You can safely put your fingers accross a 1.5 V battery because the skin resistance prevents any significant current from flowing. As shown above, it would take 1.5 kΩ just to get 1 mA. Normal skin resistance is in the 10s of kΩ at least. You can try dipping your fingers in salt water and then touching both ends of the 1.5 V battery and see if you feel anything. Again, make sure this is the fingers of the same hand. That way just in case you get any significant current it will stay local to the hand and not get to the heart or brain. You can definitely feel a 9 V battery on the tounge, but I don't know if even wet fingers is enough to feel a 1.5 V battery. If you try it, let us know.

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  • \$\begingroup\$ You can even 'taste' a 1V5 penlite cell on your tounge, touching the other end with you finger. It is safe with a 1V5 cell, but don't do the same trick with higher voltages. \$\endgroup\$ – jippie May 14 '12 at 20:46
  • \$\begingroup\$ @jippie How does that happen? One side is low resistance, but hands are higher resistance, also you add up the shortest way between your hand and tongue. I don't get it? \$\endgroup\$ – abdullah kahraman May 15 '12 at 2:56
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    \$\begingroup\$ @abdullahkahraman the tounge is much more sensitive to small currents. \$\endgroup\$ – Stefan Paul Noack May 15 '12 at 7:11
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    \$\begingroup\$ It is not so much a feeling of 'electric shock', but the battery terminal feels/tastes ... wierd. \$\endgroup\$ – jippie May 15 '12 at 7:21
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    \$\begingroup\$ @Buzai: A static electric field does little to harm your body. It is electrons moving thru you that causes the trouble. Of course it requires voltage to have current so there is a bit a chicken and egg problem. However, there are ways to show that current is what matters. You can't feel a 9V battery against a dry finger, but you can perhaps against a wet finger and definitely against your tounge. The voltage is the same in all cases, but due to different resistance the current differs. It's the current you feel. \$\endgroup\$ – Olin Lathrop May 15 '12 at 12:54

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