Hopkinson's Law describes the relationship between the reluctance of a magnetic circuit, the magnetomotive force and the magnetic flux. It is similar to Ohm's Law

Ohm's Law defines the relationship between voltage, current and resistance

It is described as

*Voltage = Current x Resistance*

Similarly, Hopkinson's Law can be written as

*Magnetomotive Force = Flux x Reluctance*

Hopkinson's Law is also known as Rowland's Law