# Is magnetic field strength directly proportional to the coil or the current?

The strength of a magnetic field won't be directly proportional to the turns in the coil. It is more correct to say that

*field strength is directly proportional to***current**through the windings of the coil. There are some "limiting factors" that will not allow this to be a hard and fast rule, but it is essentially correct.## Answer

**Magnetic field strength**(symbol:**) is defined as the magnetomotive force per unit length of a magnetic circuit. As magnetomotive force is the product of the current flowing through a winding and the number of turns, then, yes, magnetic field strength***H**is*proportional to both the current and the number of turns -but this is ONLY true over the straight part of the magnetisation curve (i.e. before it goes into saturation).