If a wire carrying current produces magnetic field around it, why its not attracted to nearby metals ? In a general household.
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Generally it’s because household cables always consist of more than one wire, and the current that goes through one returns through the other(s), creating opposing magnetic fields that cancel each other out.
Also, the attraction for a single wire is very small even with several amps of current flowing, which is why electromagnets have coils with lots of wire, in order to add together the magnetic field of every turn.
There will be an attraction.
In a household, the effect is minimal, primarily because AC is used to the magnetic direction flips 100/120 times per second and the net force is zero.
The other part is that just a single wire will not produce a lot of magnetic fields. There are a reason eclectic motors, transformers, and electromagnets have coils with the wire going in a circle many times. So even the DC in devices will not produce large magnetic fields
Yes all current through copper creates magnetic fields; but here’s the key; the field of a single straight wire with AC is too small to be seen as having an effect.
As the previous poster said, AC switches positive-negative so fast it has a net zero effect. AC also doesn’t like coiled lines, we call this inductance; the coiling of a wire creates a stronger magnetic field and when you try to run AC through a coil, the AC meets resistance in the form of the magnetic field.
Coiled DC current has a constant effect and little resistance to the flow of current.
I hope I did this right, thanks.
It is. That’s how electromagnets work. You just need to coil a lot of wire up because the effect is pretty weak at low current. If you get a few hundred amps through a wire, [the effect gets more noticeable](https://youtu.be/tUCtCYty-ns)
It does attract metals but the magnetic field is week. You need a lot of turns of wire to increase its strength.
Edit: keeping the typo for the lolz
I have worked on battery charging/jump starting equipment an electrical engineer that can be loaded to 300-400 DC amps by a load bank using individual welding cables. I have seen metal(steel) shavings and the actual cables jump on the floor when either fully loaded or unloaded by the load bank.
the electric fields are teeny-tiny, so there *is* an attraction but it’s not noticeable.
I worked one summer in an EE lab for one of my profs. My task was to measure the field strength over a linear inductive motor. (LIM). A LIM is basically a set of wire coils, which set up a magnetic field, on the ground, with a motor whose electrical frequency is synced up with field. I was trying to measure how high the voltage was a few inches above the coils.
Couldn’t get the readings. Our lab was near a busy streetcar line, which runs on 600VDC. As the cars passed by the contacts on the overhead lines, they’d generate transients which blew our readings all to hell. I was getting readings near 1-2 microvolts with no streetcars, and 10-20 when the cars were busy. A month, and we never got any useful data.
And I’d note these coils were designed to create a higher intensity field than any single wire, so the field produced by one wire would be even weaker.
It sort of is. The field will distort near conductive materials (cause a weak alignment of magnetic polarity in the metallic object) but it won’t have enough force to cause movement at the scale you want it to. The field is just too weak and the mass is too high.
If you coil the wire around the metal, so the magnetic field repeats itself and thus adds strength to the field in the dominant direction, then you can create a strong enough field to do something. This is the idea behind electromagnets.
The field loses strength with distance from the region of current (basic inverse square law; even really strong fields dissipate rapidly with distance). When coiling a wire, you keep the “new” field within the still-strong range of the next-along field, so there is more then one field involved, and the field strength adds together and extends further in the direction of coiling.
We are bathed in electromagnetic fields all the time, everywhere, and they do somewhat distort in our immediate vicinity too. The strengths of the fields is normally tiny because the power of the electromagnetism (or field generator) is relatively tiny and we are “far” from the source, so nothing really is noticeable. Need a strong internal field and almost no friction for even a needle to align to the earth’s magnetic field. A car out on the street though, isn’t going to be aligned with the earth’s field. The presence of the car, though, does modify the shape of the field in its immediate zone of influence. The changes are just so tiny, is all.
Last year was the first time I saw the copper wires move. I was fixing a short circuit in a new house, when a light switch turned on it would short and trip the breaker but right before the trip, the wires sticking out of the box would move a little.
I’ve heard about pipes in commercial banging around from that scenario but never thought I’d see it in a house.
It is. That’s one reason why you occasionally hear appliances humming; that attraction which flips with AC is constantly moving the conductors back and forth.
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