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I am pretty new to electronics, and have mainly worked with DC circuits. I'm majoring in Computer Science, but I also find electrical engineering interesting, so I am learning as much as I can. Well, my multimeter measures about 0.050 to 0.100mV when not connected to anything. As soon as I move close to the wall outlet, it creeps up to 0.1 volts, then 2 volts, then when I am pretty close to it, it reads about 4 - 6 volts. Also, when I plug one lead into the hot or neutral, why does it read 6 volts or more? And between neutral and ground, it usually reads 0.4 volts when there is minimal load on the outlet. I heard that that is normal, but is 4.4 volts from neutral to ground normal when a 1300W heater is running? Thank you for your help. I'm still learning, so these questions may sound stupid. And yes, I am taking safety precautions so that I do not get shocked.

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    \$\begingroup\$ Are you measuring AC or DC voltages? \$\endgroup\$ – Andy aka Nov 16 '15 at 9:15
  • \$\begingroup\$ I am measuring AC voltage on a wall outlet. \$\endgroup\$ – Ken Clark Nov 16 '15 at 9:15
  • \$\begingroup\$ Depending on where you live you may get 110 to 220 Vrms . So the current that your heater needs is 1300 /220 =6 A . Even a small resistance like 1 ohm could easily create 6 V drop \$\endgroup\$ – Kishore Saldanha Nov 16 '15 at 9:27
  • \$\begingroup\$ I would be concerned about 4.4v when there's a heater running if you are in a jurisdiction that mandates PME (Protective Multiple Earthing). I can't imagine earth bonding straps that would allow such a large voltage drop, without them being loose or defective in some way. If PME is not mandated in your area, then that sort of voltage could easily arise without problems. \$\endgroup\$ – Neil_UK Nov 16 '15 at 9:43
  • \$\begingroup\$ Assuming 110V and 9Ω at the heater, this basically means ~400mΩ of resistance until to the point where N and GND meeet. \$\endgroup\$ – PlasmaHH Nov 16 '15 at 10:23
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0.050 to 0.100mV when not connected to anything

This is pretty normal. It's not a big number and probably just represents the noise floor of your multimeter.

As soon as I move close to the wall outlet, it creeps up to 0.1 volts, then 2 volts, then when I am pretty close to it, it reads about 4 - 6 volts.

Also pretty normal. The electric fields emanating from house AC wiring can make a multimeter show these kind of voltages when close up. It's mainly due to the electric fields capacitively coupling to you probes with your body acting as a capacitor to ground. It would be interesting to see what the voltage drops to when you stop holding the multimeter - I would expect it to still register a number but a smaller number.

between neutral and ground, it usually reads 0.4 volts when there is minimal load on the outlet. I heard that that is normal, but is 4.4 volts from neutral to ground normal when a 1300W heater is running?

4.4 volts is certainly no un-heard of. Usually neutral is connected to earth at some point between your house and the local sub-station and given the volt drop down the neutral wire when passing several amps this would be fairly commonplace.

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  • \$\begingroup\$ Does the 4-6v reading when "close" to the outlet demonstrate the principles that a Non-contact voltage detector would use to warn a user of a live circuit? \$\endgroup\$ – JPhi1618 Nov 16 '15 at 15:17
  • \$\begingroup\$ @JPhi1618 I guess so but without looking at a circuit I can't be 100%. \$\endgroup\$ – Andy aka Nov 16 '15 at 18:02
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These days we are swimming in EM fields (Electromagnetic) and signals flying all over the place. Your multi-meter probes measure the potential difference between the 2 probes and are like receiver antennas too. With both probes just floating, you are just picking up the time averaged e-field that's in your immediate vicinity.

Most multi-meters display the RMS value of what you are measuring too.

Without a proper reference aka one probe just "floating" its possible that that probe will get "pulled up" to the probe that is touching a strong voltage and you see the difference over the internal impedance.

And as the other guys said there is coupling, inductive and capacitive. Changing magnetic fields give rise electric currents, and electric currents give rise to magnetic fields.

Still today most of electrical engineering is based on Maxwell's equations, despite quantum electrodynamics being the complete picture, we still go back to Maxwell, Faraday, Gauss and Ampere.

Theres a great website called maxwells-equations.com which gives a great overview of the 4 great equations, without being too scary with the maths.

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