Inductive and capacitive terms

Question

What it means when we say that some component or device is inductive or capacitive? How these terms are related to capacitors and inductors?

From what perpective? Physic, power application, RLC? There is so much to talk about here. — MathieuL, Jul 21 '15 at 18:55
if the most general term, a capacitor component is a component that will stock the energy into a electric field and a inductive component will stock the energy into a magnetic field. — MathieuL, Jul 22 '15 at 14:22
If you are interested i can post a answer that talk about these element but from the electromagnetic perspective. — MathieuL, Jul 22 '15 at 14:26
I will post this night, I need to recheck some electromagnetic books. — MathieuL, Aug 04 '15 at 12:51

score 16 · Accepted Answer · edited Aug 05 '15 at 06:55

A component, device or circuit would be said to be inductive if, upon application of DC voltage, the current through or into the component, device or circuit rises with any delay in comparison to the rise of voltage applied to the component, device or circuit.

A component, device or circuit would be said to be capacitive if, upon application of DC voltage through a series resistance, the voltage at the input of the component, device or circuit rises with any delay in comparison to the rise of current through or into the component, device or circuit.

If an AC voltage is applied, any lag in current compared to voltage would indicate an inductive component and any lag in voltage compared to current would indicate a capacitive component.

Note that the delay can be any delay for an inductive or capacitive component that is not an ideal inductor or capacitor while in an ideal capacitor or inductor, the delay is 90 degrees of a sine wave.

I should add that a component, device or circuit could be exhibit either inductive or capacitive characteristics depending to frequency.

EDIT: Additional attention is being sought for this question. I could add that when we say that some component is inductive or capacitive, that would generally mean that inductance or capacitance is predominant in the behavior of that device. The operating frequency of the circuit is an important factor in determining what characteristic is predominant.

Peter Smith has provided quite a bit about ESR and ESL. Capacitors can also have effective or equivalent parallel resistance. That accounts for self discharge or leakage of capacitors that are not connected to a circuit or passage of DC current that the capacitor is intended to block.

I don't think that it's appropriate in this forum to try to develop a discussion about the theory and application of inductance and capacitance. If more is needed, I think additional specific questions may be required.

score 4 · Answer 2 · answered Jul 21 '15 at 14:03

A capacitor is a device specifically designed to have capacitance; likewise an inductor is specifically designed to have inductance. For a capacitor, this means we are exploiting electrostatics for a useful part, and for an inductor, we are exploiting magnetics for a useful part.

In a real component that is not an inductor, there will still be some self-inductance, and likewise there will actually be some parallel capacitance.

A real capacitor will have an Effective Series Inductance (usually abbreviated esl), and a real inductor will have an effective parallel capacitance (and inter-winding capacitance).

In addition, each will also have an effective series resistance.

A resistor will have an esl and an effective capacitance, and indeed all passive components are in fact RLC circuits, although the effects may not be of interest in many applications.

If we consider that capacitance exists between any two points of differing electrical potential and that self-inductance exists in any current carrying item, things become a bit clearer.

We would normally use the terms 'capacitive' and 'inductive' in relation to components where the effects of each must be taken into account and it is not apparent from the symbol that the part may operate in an inductive or capacitive mode.

As an example, decoupling capacitors in very high speed systems are in fact inductive at those frequencies (they have a self-resonance at 1/2pi sqr(LC) where L is the self-inductance of the part). The typical self-inductance of an 0805 surface mount capacitor is about 1.1nH

Above this frequency, the self-inductance of the part dominates its response, and would therefore be termed 'inductive' at those frequencies, even though it is patently not (deliberately) an inductor.

HTH

score 1 · Answer 3 · answered Aug 04 '15 at 10:24

In very basic terms: Inductive components (Inductors), resist change in current. While capacitive components (Capacitors), resist change in voltage.

Both types can be used for all kinds of filtering methods (HP, LP, etc.).

Capacitive and inductive components also introduce a phase shift. They are not considered to have a resistance, but a reactance. This is the imaginary component of impedance (impedance = resistance + j*reactance). Where j is the imaginary unit.

Best of luck!

score 1 · Answer 4 · answered Aug 05 '15 at 05:26

If a component of a device is capacitive, it tends to exhibit the following characteristics,

In a dc perspective, it essentially means that it restricts the change in voltage in the parallel branch in which capacitive behaviour is observed. Moreover the current in the branch increases in a exponential fashion. And also the component becomes an open circuit in a very short span of time, because the capacitor will build up a voltage equal to the voltage across its parallel branch.

For more reading on dc capacitors visit, http://www.allaboutcircuits.com/textbook/direct-current/chpt-13/electric-fields-capacitance/

In an ac perspective, it essentially means that at low frequencies the capacitive component tends to open circuit itself, whereas at high frequencies it becomes a short circuit. It also makes the voltage lag current by 90 degree.

For more reading on ac capacitors visit,http://www.allaboutcircuits.com/textbook/alternating-current/chpt-4/ac-capacitor-circuits/

If a component in a device is inductive, it tends to exhibit the following characteristics,

In a dc perspective, it essentially means that it restricts the change in current in the branch in which capacitive behaviour is observed. Moreover the voltage in the branch increases in a exponential fashion. And also the component becomes an short circuit in a very short span of time, because the inductor will build up a current equal to the current in its branch.

For more reading on dc inductors visit,http://www.allaboutcircuits.com/textbook/direct-current/chpt-15/magnetic-fields-and-inductance/

In an ac perspective, it essentially means that at high frequencies the inductive component tends to open circuit itself, whereas at low frequencies it becomes a short circuit. It also makes the current lag voltage by 90 degree.

For more reading on ac inductors visit,http://www.allaboutcircuits.com/textbook/alternating-current/chpt-3/ac-inductor-circuits/

How are inductor and capacitors related?

If you know about the duality principle, you should have an answer to this. From what I said above it can be seen that for a capacitor

I=C(dv/dt) where C is the capacitance of the capacitor.

In the above expression if you are going to change the Parameters I to V and C to L, where L is the inductance of the inductor you get the equation of the inductor,

V=L(di/dt) where L is the inductance of the inductor.

They are essentially duals in nature. Capacitor becomes an inductor if you are going to change the parameters of it. https://en.wikipedia.org/wiki/Duality_(electrical_circuits)

Inductive and capacitive terms

4 Answers4