# what does negative inductance mean?

Status
Not open for further replies.

#### zirtapoz

##### Full Member level 3
positive capacitance negative

i think we r talking about inductance(L) not reactance. So who wants to explain me energy stored in an inductor (w=.5*L*I²) ??

this means that negative inductance causes negative energy stored in inductor!!

there r some arguiing about this in physics.. For anyone interested refer:

https://www.physicsforums.com/archive/index.php/t-167245.html

#### LvW

##### Advanced Member level 5
neative inductance

zirtapoz said:
i think we r talking about inductance(L) not reactance. So who wants to explain me energy stored in an inductor (w=.5*L*I²) ??
this means that negative inductance causes negative energy stored in inductor!!
l

I don´t think that we have a "logical" or a physical problem with a negative inductance.
The reason is that we have a kind of simplified wording to speak of a "negative" inductance. In fact, we mean that there is a minus sign in the equation desribing the relation between voltage and current: v=(-1)*Ldi/dt.
Thus, the factor (-1) forces the current to lead the voltage by 90 deg. That´s all.
As before, L is still a factor determined by external conditions and can be regarded as positive - without any problems with energy definition. But in this case we must not forget to allocate the minus sign to the expression di/dt.
Of course, by deriving the formula given above we have to change the direction of the current (or of the voltage) from the beginning if we try to describe a part which has the properties which we call "negative" inductance.

#### ashish_chauhan

##### Full Member level 5
gamma=sqrt(z.*y)

LvW said:
zirtapoz said:
i think we r talking about inductance(L) not reactance. So who wants to explain me energy stored in an inductor (w=.5*L*I²) ??
this means that negative inductance causes negative energy stored in inductor!!
l

I don´t think that we have a "logical" or a physical problem with a negative inductance.
The reason is that we have a kind of simplified wording to speak of a "negative" inductance. In fact, we mean that there is a minus sign in the equation desribing the relation between voltage and current: v=(-1)*Ldi/dt.
Thus, the factor (-1) forces the current to lead the voltage by 90 deg. That´s all.
As before, L is still a factor determined by external conditions and can be regarded as positive - without any problems with energy definition. But in this case we must not forget to allocate the minus sign to the expression di/dt.
Of course, by deriving the formula given above we have to change the direction of the current (or of the voltage) from the beginning if we try to describe a part which has the properties which we call "negative" inductance.

Fantastic!!!

Status
Not open for further replies.