Question

1. in figure a, when electrons move in the coiled wire what is produced? magnetic field, electromagnet
2. in figure a, if you changed the direction of electron - flow by switching the connections to the battery, what would happen?
3. in figure a, if an iron bar were inserted into the wire coil, what would happen to the iron bar?
4. suppose you wrapped an iron bar with wire and connected the ends of the wire to a battery. what is this device called? what would happen to this device if you disconnected the battery?

Explanation:

Step1: Recall electromagnetic - induction principle

When electrons move in coiled wire in a magnetic field, an electromagnet is produced due to the magnetic - field generated by the electric current in the wire.

Step2: Understand the effect of current direction change

Changing the direction of electron flow (current) by switching battery connections will reverse the polarity of the electromagnet. The north and south poles of the magnetic field generated by the coil will swap.

Step3: Analyze iron - bar insertion

When an iron bar is inserted into the wire coil, the iron bar will become magnetized. The magnetic domains in the iron bar will align with the magnetic field of the coil, making the iron bar an induced magnet.

Step4: Identify the device and its behavior

Wrapping an iron bar with wire and connecting to a battery creates an electromagnet. If the battery is disconnected, the electric current stops flowing, and the magnetic field of the coil collapses. The iron bar will lose its magnetization (or retain a very weak residual magnetization in some cases) as there is no longer an external magnetic - field source from the current - carrying coil.

Answer:

1. An electromagnet is produced.
2. The polarity of the electromagnet will reverse.
3. The iron bar will become magnetized.
4. The device is an electromagnet. If the battery is disconnected, the iron bar will lose its magnetization (or have a very weak residual magnetization).