a solenoid) produces a magnetic field. This works in free space, but if the solenoid is wrapped around a ferromagnetic core such as soft iron the effect of the field is greatly amplified. This is because the internal magnetic domains of the material align with each other to greatly enhance the magnetic flux density. Equations Using Ampère's circuital law, it can be shown that the magnetic flux density induced by a solenoid of effective length with a current through loops is given by the equation: The force between the electromagnet and the armature plate with surface area exposed to the electromagnet is given by the equation: In both equations, represents the permeability of free space and the relative permeability of the core. Although the actual performance of a magnetic lock may differ substantially due to various losses (such as flux leakage between the electromagnet and the conductor), the equations give a good insight into what is necessary to produce a strong magnetic lock. For example, the force of the lock is proportional to the square of the relative permeability of the magnetic core. Given the relative permeability of a material can vary from around 250 for cobalt to around 5000 for soft iron and 7000 for silicon-iron, the choice of magnetic core can therefore have an important impact upon the strength of a magnetic lock. Also relevant is the choice of current, number of loops and effective length of the electromagnet. Technical comparison Magnetic locks possess a number of advantages over conventional locks and electric strikes. For example, their durability and quick operation can make them valuable in a high-traffic office environment where electronic authentication is necessary. Advantages Remote operation: Magnetic locks can be turned on and off remotely by adjusting the power source.. Easy to install: Magnetic locks are generally easier to install than other locks since there are no interconnecting parts. Quick to operate: Magnetic locks unlock instantly when the power is cut, allowing for quick release in comparison to other locks. Sturdy: Magnetic locks may also suffer less damage from multiple blows than do conventional locks. If a magnetic lock is forced open with a crowbar, it will often do little or no damage to the door or lock. There are no moving parts in an electromagnetic lock to break. Disadvantages Requires a constant power source in order to be secure. Can de-energize in the event of