Unit of inductance—self-inductance and mutual inductance—is Henry (H). It is named after the American physicist Joseph Henry. Most electrical coils have inductance properties. The change in the electric current or flux induces EMF in a coil. This property is called inductance.
The magnitude of induced EMF is proportional to the rate of change of the electric current. The higher rate of change of current causes more flux. As a result, more EMF induces in a coil.
The S.I unit of the inductance is Henry H. Its MKS unit is Kg m² s⁻² A⁻².
Definition of Inductance and Its SI Unit
Inductance is the property of a coil or circuit that opposes any change in electric current by inducing an electromotive force (EMF). In simple terms, it is the ability of a coil to store energy in the form of a magnetic field.
When a coil receives an alternating current, the flux induces in a coil. The varying flux induces EMF in a coil.
The SI unit of the inductance property is Henry (H). It defines how much EMF is induced for a given rate of change of current. One Henry means that a change of 1 ampere per second produces an induced EMF of 1 volt in the coil.
Formula of Inductance in Terms of Henry
The following formula shows the relationship between induced EMF and the rate of change of current. It helps define the unit of inductance precisely.
From the above formula of inductance, if one volt induces in a closed circuit or a coil by variation of alternating current of 1 ampere per second, then the self-inductance of a coil is one Henry. In other words, 1 H = 1 V·s/A.
Henry in Weber per Ampere Form
We can express Henry in another form as given below. For example, 1 Henry can also be written as one weber per ampere (Wb/A).
Unit of Mutual Inductance
In the case of two coils mutually coupled, the mutual inductance of the coils is as below;
The mutual inductance(M) of mutually coupled coils is one henry if a varying current of 1 ampere per second in one coil induces one volt in another coil. This shows that the Henry is valid for both self and mutual inductance.
Thus, the SI unit of mutual inductance is Henry(H).
Other Units of Inductance
Henry is the big unit of inductance. There are other smaller units of inductance, such as:
- millihenry (mH)
- microhenry (μH)
- nanohenry (nH)
- picohenry (pH)
The inductance of a coil having a value in the order of millihenry (mH) and microhenry (μH) has wide applications for radio and audio frequency range.
The inductance of a coil having a value in the order of nano-Henry(nH) has wide applications for a very high-frequency range.
Relation between the Different Units of Inductance
| Units of Inductance | Equivalent in Henry (H) |
| 1 millihenry (mH) | 10⁻³ H |
| 1 microhenry (μH) | 10⁻⁶ H |
| 1 nanohenry (nH) | 10⁻⁹ H |
| 1 picohenry (pH) | 10⁻¹² H |
Conclusion: The Unit of Inductance is Henry (H)
Thus, the SI unit of inductance is Henry (H). It can also be written as volt–second per ampere (V·s/A) or weber per ampere (Wb/A). In real circuits, engineers often use smaller units such as millihenry (mH), microhenry (μH), and nanohenry (nH). These are common in applications ranging from audio electronics to high-frequency communication systems.
FAQs on Unit of Inductance
The SI unit of inductance is Henry (H).
1 Henry = 1 volt induced when the current changes at 1 ampere per second (1 H = 1 V·s/A).
mH (10⁻³ H), μH (10⁻⁶ H), nH (10⁻⁹ H), pH (10⁻¹² H).
Yes, 1 H = 1 Wb/A.
Joseph Henry, an American physicist.
Inductance is measured in Henry (H), which is the standard SI unit.
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