Timeline for How can current flow in an AC-inductor circuit if the source voltage is always exactly countered by the inductor's back-EMF?
Current License: CC BY-SA 4.0
10 events
| when toggle format | what | by | license | comment | |
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| Apr 10 at 14:16 | comment | added | G36 | Voltage is induced across an inductor only when the magnetic field is changing. If there is no change in the magnetic field, no voltage will be induced across the inductor. The magnetic field changes only when the current is also changing. Therefore, to generate voltage across an inductor, the applied current must vary. If the current remains constant, no voltage will be induced, regardless of its magnitude. In other words, the very existence of induced voltage depends on the fact that current changes, and it must change. | |
| Apr 10 at 10:33 | vote | accept | cloud | ||
| Apr 10 at 7:49 | answer | added | Andy aka | timeline score: 0 | |
| Apr 10 at 4:18 | answer | added | MarkU | timeline score: 0 | |
| Apr 10 at 2:58 | comment | added | Tony | Well it is a /differential/ equation. Current will initially be very tiny, infinitesimal even but that's enough to get things started. From the same calculus that brought you zero-limit-thing divided by zero-limit-thing is finite (derivative) and infinite sum of infinitesimal is finite (integral). | |
| Apr 10 at 2:54 | comment | added | cloud | @Tony My question is about how these changing magnetic fields can exist in the first place. They arise due to changing currents in the coil, and one of the first things one is taught about electricity is that current flows because of a potential difference. If the EMF and applied voltage always exactly counter each other, the PD between any point on the circuit and the positive terminal of the source is the negative of the PD between that point and the positive of the coil, meaning net current is zero. How, then, can current start flowing? (Deleted previous comment because of mistake) | |
| Apr 10 at 2:41 | answer | added | Math Keeps Me Busy | timeline score: 0 | |
| Apr 10 at 2:35 | comment | added | Tony | The e.m.f. that opposes the applied voltage is the result of a changing magnetic field in the coil, but the magnetic field in the coil is only changing because the current through the coil is changing. If there were no current there would be no e.m.f. and so nothing to oppose the applied voltage, which means there would be lots of current (so this is inconsistent and cannot be the solution). The differential equation gives the correct answer. | |
| S Apr 10 at 1:30 | review | First questions | |||
| Apr 10 at 4:25 | |||||
| S Apr 10 at 1:30 | history | asked | cloud | CC BY-SA 4.0 |