Can anybody explain why my tongue gets a reading on a multimeter. Do I have a current? Why do i have resistance? Why do some things have resistance? I am very confused.
3 Answers
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You might find Conduction of Electrical Current to and Through the Human Body: A Review interesting.
An excerpt from paragraph Skin resistance protects the body from electricity:
The body has resistance to current flow. More than 99% of the body's resistance to electric current flow is at the skin. Resistance is measured in ohms. A calloused, dry hand may have more than 100,000 Ω because of a thick outer layer of dead cells in the stratum corneum. The internal body resistance is about 300 Ω, being related to the wet, relatively salty tissues beneath the skin.
This is also the reason why your tongue has a not so high resistance.
answered Nov 8, 2019 at 12:07
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Setting your multimeter to measuring resistance (ohm) it will read somewhere between some kilo ohms and up to more than a mega ohm depending on how your are holding the probes. Moist fingers will result in lower contact resistance.
Many materials including your body will have some resistance and will be able to conduct current.
Moving on to voltage; your muscles including your heart will have a tiny measurable voltage across them when they are moving your arm or pumping blood around your body. This is why a ECG can measure your heart rates, as the different muscles of your heart is activated at every heart beat.
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1\$\begingroup\$ Amusing anecdote : In a factory, the paint shop foreman had exceptionally dry skin on his hands from years of handling paint, thinners, turps etc. So much so that he could grab a pair of live mains wires with impunity. The maintenance electricians even used to ask him to test wires for them before they started work, and sometimes, out of devilment, he would lie! \$\endgroup\$ Commented Nov 8, 2019 at 13:12
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You do have some currents inside you, mostly in your nerves and muscles. But these are tiny, and not what the multimeter is measuring.
The multimeter measures resistance by using its battery to apply a low voltage between the two probes, and seeing if a current flows. Lots of current means a low resistance. Little or no current means a high resistance.
The resistance of a substance depends on how many free charge carriers there are in it, where "free" means able to move around in the substance and "charge carriers" are usually electrons, but could be positive or negative ions.
Plastic, glass and similar substances have very few free electrons, and so a very high resistance. Metals have lots of free electrons, and so have a low resistance.
You are essentially a bag of slightly salty water, with bones inside to keep you the right shape. The ionic salts produce positive and negative ions when dissolved in water. This makes you an electrical conductor, albeit with a fairly high resistance.
