An engineering student is designing a miniature electromagnetic relay for an automated control circuit. The relay uses an electromagnet to attract a pivoting armature to close a switch.
Describe the construction of the electromagnet required for this relay.
When testing the relay with different prototype armatures, the student finds that an armature made of soft iron releases instantly when the coil's current is switched off. However, an armature made of hardened steel remains held against the core even after the current is cut. Explain these observations, referring to the magnetic properties of soft iron and steel.
