3. Using the theory of magnetic domains, what correctly describes the characteristics of the magnetic domains of the three materials below (i.e. which one is non-magnetic, had magnetic domains but not magnetized, which one is magnetized)? C. Reduce the number of turns. D. Insert an iron bar into the solenoid. B. Increase the voltage.

# Question 3 Explanation:Magnetic domains are regions within a material where the magnetic moments of atoms are aligned in the same direction. The characteristics of magnetic domains differ depending on the type of material and its magnetic properties. There are generally three categories of materials based on their magnetic properties:1. Non-magnetic materials: These materials do not have magnetic domains that align in a significant way. Their atomic magnetic moments are randomly oriented, canceling each other out, resulting in no net magnetic field. Examples include wood, plastic, and many other materials that do not respond to a magnetic field.2. Materials with magnetic domains but not magnetized: These are typically ferromagnetic materials that have magnetic domains, but the domains are randomly oriented so that the material as a whole does not exhibit a net magnetic field. When an external magnetic field is applied, the domains can become aligned, and the material can become magnetized. Examples include un-magnetized iron, nickel, and cobalt.3. Magnetized materials: These are materials where the magnetic domains are aligned in the same direction, resulting in a net magnetic field. This can occur naturally or after exposure to an external magnetic field which causes the domains to align. Once the external field is removed, the material retains its magnetization. Examples include permanent magnets like those made of magnetite or artificially magnetized ferromagnetic materials.# Question 3 Answer:- Non-magnetic material: The material with no net magnetic field due to randomly oriented magnetic moments.- Material with magnetic domains but not magnetized: The material that has magnetic domains which are not aligned, resulting in no net magnetic field in its natural state.- Magnetized material: The material with magnetic domains that are aligned, resulting in a net magnetic field.# Question 4 Explanation:To determine which modification would decrease the magnetic field inside of a solenoid, we need to understand the factors that affect the strength of the magnetic field in a solenoid. The magnetic field inside a solenoid is given by the formula: where:- is the magnetic field,- is the permeability of the core material,- is the number of turns per unit length of the solenoid,- is the current through the solenoid.From this formula, we can see that the magnetic field is directly proportional to the current and the number of turns per unit length . Therefore, increasing the voltage (which would increase the current ) would increase the magnetic field, not decrease it. Reducing the length of the solenoid without changing the number of turns would increase , the number of turns per unit length, and thus increase the magnetic field. Inserting an iron bar into the solenoid would increase , the permeability, and thus increase the magnetic field.The only option that would decrease the magnetic field is to reduce the number of turns , as this would directly decrease the number of turns per unit length if the length of the solenoid remains constant.# Question 4 Answer:C. Reduce the number of turns.