Home / Topics / Magnetism & Induction
Mutual inductance
Intermediate
Changing current in one coil induces emf in another.
M = Φ₂/I₁A changing current in one coil induces an EMF in a nearby coil: ε₂ = −M dI₁/dt. M depends on geometry and coupling.
Wireless charging uses mutual inductance.
M₁₂ = M₂₁.
In more detail
Mutual inductance M describes how a changing current in one coil induces an emf in another nearby coil. It is the basis of transformers and wireless charging.
Real-world uses
- Transformers use mutual inductance to step voltage up or down.
- Wireless phone chargers transfer energy by mutual inductance.
- A transformer and wireless charging pads transfer energy between two coils through their mutual inductance.
Open the interactive lesson, with simulation and quiz →
Frequently asked questions
What determines M?
The geometry of the coils and how much flux links them.
Can mutual inductance be zero?
Yes, if the coils are placed so their fields do not link.
What determines mutual inductance?
The geometry of the coils and how well the flux from one links the other.
Related topics in Magnetism & Induction
Self-inductance · Inductance of a solenoid · Energy in an inductor · Transformer · Transformer losses · AC generator