Can someone please explain what is probaly a very stupid question but it does puzzle me, i am an ex house electrician now working in a factory faultfinding in panels.
Why do AC coils, AC electromagnets not chatter in and out due to the changing magnetic field?

Thanks in advance....

 

Most likely as they have a shader pole. It is generally a copper slug around the armature on one end. It prevents the magnetic field from going to 0 when the polarity of the AC voltage reaches near 0 volts and changes polarity. Most relays and or solenoids can have a relative large change in applied voltage without causing them to deenergize.