Question

The diagram shows the set-up for an electric doorbell.

At bottom, a doorbell. Starting from midright, a wire attached to a contact screw runs to a power source and then to a bell and then to coil around both arms of a U shaped iron core. The coils plus core is labeled electromagnet with the lower arm of the core labeled N and the upper arm labeled S. The wire emerges from the coils to attach to a steel bar at its top end. The bottom end of the steel bar has a short piece of wire leading to a striker.
Which best explains why the bell would not ring in this set-up?

The circuit is open.
The electromagnet has an iron core.
The circuit is closed.
The electromagnet is made of steel.

Answer 1

The electromagnet is made of steel.

Steel is a hard magnetic material and would retain magnetism, so the armature (striker) would stick to it and not pull away to make the intermittent contacts needed for ringing. Electric bells use soft iron cores (which demagnetize quickly) so the armature can release and oscillate.