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I think I must have missed something when going over inductors for my electric circuits class.
The voltage across an inductor is described by the equation: ##V(t) = L\frac{di(t)}{dt}##
For the case where current is flowing through the inductor until ##t=0##, at which point the voltage/current supply is switched off, the voltage then takes the form: ##V(t) = L\frac{de^{\frac{-t}{\tau}}}{dt} = -L{\tau}^{-1}e^{\frac{-t}{\tau}}##
My question is, why is this voltage negative? Wouldn't that oppose the current flow? Obviously I'm not understanding something, as this appears to contradict the fact that an inductor opposes changes in current. I thought the voltage would be a positive number, so as to continue current flow in its current direction.
The voltage across an inductor is described by the equation: ##V(t) = L\frac{di(t)}{dt}##
For the case where current is flowing through the inductor until ##t=0##, at which point the voltage/current supply is switched off, the voltage then takes the form: ##V(t) = L\frac{de^{\frac{-t}{\tau}}}{dt} = -L{\tau}^{-1}e^{\frac{-t}{\tau}}##
My question is, why is this voltage negative? Wouldn't that oppose the current flow? Obviously I'm not understanding something, as this appears to contradict the fact that an inductor opposes changes in current. I thought the voltage would be a positive number, so as to continue current flow in its current direction.