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 Mar 3 awarded Notable Question Feb 23 awarded Popular Question Jan 2 comment What happens when we connect a metal wire between the 2 poles of a battery? I was looking for a clear explanation of how exactly electric fields appear along a circuit connected to a battery. This explanation is exactly what I was looking for. Aug 10 awarded Benefactor Aug 10 comment Rotational speed of a coil in a uniform magnetic field at equilibrium Thank you for your help. This solution makes sense. As you said, this question seems to be poorly constructed, giving rise to many interpretation doubts. Therefore, many assumptions which are not stated in the question were needed in order to reach a solution that is close to the book's answer. Aug 10 comment Rotational speed of a coil in a uniform magnetic field at equilibrium Thank you for the answer. But I have another question: when you wrote that, if the motor has a commutator, $\langle \sin \theta \rangle \not = 0$, did you mean to say that only non-negative values of sine will be used, because torque doesn't change direction? Aug 10 revised Rotational speed of a coil in a uniform magnetic field at equilibrium added 539 characters in body Aug 9 comment Rotational speed of a coil in a uniform magnetic field at equilibrium @kleingordon: OK, I get it now. The only point that I am still missing is why exactly $\sin\theta$ has to equal $1$ for this to be true. Aug 8 comment Rotational speed of a coil in a uniform magnetic field at equilibrium Thank you for the reply. So, this equilibrium that the question is referring to is an instantaneous equilibrium, like @kleingordon said, rather than a permanent state of equilibrium? When you wrote $NAB\omega\sin\theta$ becomes zero, did you mean to say that $24 - NAB\omega\sin\theta$ becomes zero? Actually I think that I don't still quite understand how this makes the torque become zero. Aug 8 comment Rotational speed of a coil in a uniform magnetic field at equilibrium Thank you for the answer. But I don't quite see why $\sin \theta$ would necessarily stay equal to 1 in this case, because the motor continues to rotate. Aug 5 awarded Promoter Jul 25 awarded Student Jul 23 revised Rotational speed of a coil in a uniform magnetic field at equilibrium deleted 2 characters in body Jul 19 revised Rotational speed of a coil in a uniform magnetic field at equilibrium added 6 characters in body Jul 18 awarded Tumbleweed Jul 13 awarded Supporter Jul 12 awarded Editor Jul 11 revised Rotational speed of a coil in a uniform magnetic field at equilibrium added 22 characters in body Jul 11 asked Rotational speed of a coil in a uniform magnetic field at equilibrium