If an electric current is flowing through an electric wire, can we consider that wire charged?
The answer is required with a proof. Can we consider the wire to be charged positively or negatively?
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asked Mar 8, 2014 at 7:07
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5 Answers
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Jerk_dadt is correct. Electric current is the flow of free electrons in the conductor. At any instant, the number of electrons leaving the wire is always equal to the number of electrons flowing from the battery into it. Hence, the net charge on the wire is zero.
If you say the current carrying conductor is charged, it will violate the Kirchoff junction rule, which is based on the fact that in an electric circuit, a point can neither act as a source of charge, nor can the charge accumulate at that point.
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$\begingroup$ There are no free electrons . All the electrons are in place. The battery forces them out of their weakly held positions and along. $\endgroup$– RichieHHCommented Sep 19, 2019 at 6:20
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$\begingroup$ Kirchhoff's laws are a bit incorrect in general. At any instant in time, the current entering a transmission line is in general NOT equal to the current exiting that same line; this "violates" Kirchhoff's current law. $\endgroup$ Commented Jun 10, 2020 at 4:30
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$\begingroup$ Also, wires can indeed obtain a net charge. When modeling transmission lines, the shunt capacitance considers that effect. $\endgroup$ Commented Jul 17, 2021 at 20:25
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No, not necessarily. Current is the just the movement of electrons already in the wire (that is neutral). The electric field (or voltage) applied causes them to have a net movement in one particular direction (i.e. opposite direction of conventional current).
So copper has 29 protons and 29 electrons per atom. A copper wire would have a net zero charge. It conducts electricity very well because its outer electrons can move "freely" through the wire since they are loosely bound. There is no net charge involved here (for either positive or negative charge).
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$\begingroup$ No. They don't move freely. They are pushed. Without a voltage they sit quite happily and move nowhere. $\endgroup$– RichieHHCommented Sep 19, 2019 at 6:18
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See charge current continuity equation.
Del on Current Density = change in charge per unit of volume.... Current Density = conductivity * Electric Field
What this means is that any time we have a divergence in the electric field, we will have a violation of Kirchhoff's Junction Law, or in other words, we will have a local accumulation of charge. Note, charge is STILL GLOBALLY conserved, however not locally. So where do we observe divergence in the electric field? We observe divergence in the electric field if we have currents running through materials of non-uniform composition, currents running across interfaces of different materials, conductors with currents running through non uniform geometries and on wave fronts where there are voltage fluctuations propagating down the line.
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It depends. Is the electric current flowing briefly in a circuit that contains a large capacitor? None of the other answers seem to have contemplated this possibility.
If it is a steady current through a resistor, definitely the answer is no.
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yes exactly a wire is neutral before it is connected with a battery and will be again neutral cause battery supplies the number of electrons that are flowing in the circuit.
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1$\begingroup$ It's difficult to understand what is meant by "battery supplies the number of electrons that are flowing in the circuit." Can you clarify? $\endgroup$ Commented Jun 26, 2015 at 3:33
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$\begingroup$ For electrons to be forced down the wire they need to be replaced by other electrons.. From the battery. $\endgroup$– RichieHHCommented Sep 19, 2019 at 6:19