Answer:
An electromagnet is a type of magnet that is created by an electric current flowing through a coil of wire wrapped around a magnetic core. The core is usually made of a ferromagnetic or ferrimagnetic material, such as iron, that can increase the magnetic field strength by hundreds or thousands of times.
The effects on an electromagnet of removing or replacing the core depend on the properties of the core material. Here are some possible effects:
i) Removing the core: This will reduce the magnetic field strength of the electromagnet, as the core material is no longer concentrating the magnetic field lines. The electromagnet will become an air-core coil, which has a much lower magnetic permeability than a ferromagnetic or ferrimagnetic core. The electromagnet will also lose its ability to retain some magnetism when the current is switched off, as the core material is no longer magnetized.
ii) Replacing the iron core with a steel core: This will change the magnetic field strength and the magnetic behavior of the electromagnet, depending on the type and quality of steel used. Steel is an alloy of iron and other elements, such as carbon, manganese, nickel, chromium, etc. Some types of steel have higher magnetic permeability than iron, which means they can increase the magnetic field strength more than iron. However, some types of steel have lower magnetic permeability than iron, which means they can decrease the magnetic field strength. Steel also has higher coercivity and hysteresis than iron, which means it can retain more magnetism when the current is switched off, but it also requires more energy to magnetize and demagnetize. Steel can also be affected by temperature changes, corrosion, and mechanical stress, which can alter its magnetic properties over time.