Wikipedia:Reference desk/Archives/Science/2021 November 29

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November 29

How can a magnet be used to alter a current?

Current through a circuit, like a flashlight, and current through a wire? So that's DC and AC. Magnets can interfere with the electromagnetic field, right. 67.165.185.178 (talk) 05:27, 29 November 2021 (UTC).

That's right. Dynamos and Power stations use magnets to generate electrical current. Do you have a more specific question?--Shantavira|^{feed me} 09:22, 29 November 2021 (UTC)

Yea, but I don't think electric current is the word I'm looking for, that makes it seems like magnets create or destroy electricity from nothing. 67.165.185.178 (talk) 14:01, 29 November 2021 (UTC).

Electric power plants make electricity by spinning one or more magnets near large amounts of wire, if the motion stopped the electricity would turn off. Sagittarian Milky Way (talk) 17:17, 29 November 2021 (UTC)

Okay, now I know what my communication problem was. I'm talking about placing a magnet near it, not placing a spinning magnet near it. 67.165.185.178 (talk) 09:04, 30 November 2021 (UTC).

There's the Hall effect. PiusImpavidus (talk) 09:49, 30 November 2021 (UTC)

If you have a battery making 1 volt and amp at the Hall conductor and create the Hall effect with a static permanent magnet and try to get extra power from the Hall effect with a second loop of wire will it work? Does the battery circuit have to reduce wattage to keep the sum of the 2 circuits from exceeding 1 watt and breaking conservation of energy? Sagittarian Milky Way (talk) 15:17, 30 November 2021 (UTC)

It still has to move, if you are making enough electricity you will feel resistance, that's where the energy comes from. Sagittarian Milky Way (talk) 14:43, 30 November 2021 (UTC)

Resistance, from a spinning or non-moving magnet? 67.165.185.178 (talk) 14:51, 30 November 2021 (UTC).

If you wave a conductive armillary sphere back and forth near a powerful enough magnet it'll push back like it wants to be static. Sagittarian Milky Way (talk) 15:17, 30 November 2021 (UTC)

Whether the current is DC or AC depends on the power source. Flashlights typically operate on batteries, which are used to power DC circuits. The current through a wire can be of either type. Faraday's law of induction describes how a magnetic field interacts (a more neutral term than "interferes"; the interaction can be useful) with an electric circuit. It requires the magnetic flux to vary in time. A stationary permanent magnet has no effect on a stationary electric circuit.  --Lambiam 11:31, 29 November 2021 (UTC)

Weird, I thought magnets influence DC motors more than AC motors? 67.165.185.178 (talk) 14:01, 29 November 2021 (UTC).

What kind of influence are you thinking of? Among electrical motors, the difference between motors powered by DC sources and AC sources is slight; the former type has an additional commutator that makes the direct current appear to the coils of the motor as if it alternating. It is not apparent to me why that difference should be of any importance when magnet enter the scene.  --Lambiam 23:51, 29 November 2021 (UTC)

Okay here's an answer I got from a retired electrical engineer: for dc motors, the magnetic flux lines have to intersect a coil of wire at the correct angle at a certain rate of speed, while alternating north and south poles to excite electrons in the wire coil to create measurable current flow. a motor just reverses the process. ac motors are a little different. alternating current is always rising and falling the magnet would have to be synchronized in reversing poles to affect the ac motor. 67.165.185.178 (talk) 05:53, 30 November 2021 (UTC).

@Sagittarian Milky Way: Here is what the retired electrical engineer responded to your question to PiusImpavidus: hall effect devices are simply a magnetic switch in a solid state form. essentially an electronic reed switch. it's a make or break device. not capable of making current or voltage, merely to control it. can use it to control a circuit such as a servo feedback sensor or like in a car engine for crankshaft position sensor. 67.165.185.178 (talk) 19:06, 1 December 2021 (UTC).