Question

A ferromagnetic substance becomes a permanent magnet when it is placed in a magnetic field because (a) all the domains get oriented in the direction of magnetic field. (b) all the domains get oriented in the direction opposite to the direction of magnetic field. (c) domains get oriented randomly. (d) domains are not affected by magnetic field.

Short answer

A ferromagnetic substance becomes a permanent magnet when placed in a magnetic field because (a) all the domains get oriented in the direction of the magnetic field.

Step-by-step solution

Understanding Ferromagnetism

Ferromagnetism is the basic mechanism by which certain materials, like iron, form permanent magnets. This occurs when the magnetic moments of atoms in a ferromagnetic substance align to form a magnetic domain.

Role of Magnetic Domain Orientation

When a magnetic field is applied to a ferromagnetic material, the domains become aligned with the field. The more the domains are aligned, the stronger the magnetism of the material.

Determining the Correct Option

Since the domains align with the magnetic field to create a permanent magnet, we can conclude that option (a) 'all the domains get oriented in the direction of the magnetic field' is the correct answer.

Key concepts

Magnetic Field

The concept of a magnetic field is essential for understanding how materials like ferromagnets interact with their surroundings. Imagine a magnetic field as an invisible force that permeates space wherever a magnetic force is present. This field can be visualized by the familiar pattern of iron filings on paper above a magnet, which shows the directional pathways that the magnetic force follows. These pathways emerge from the north pole of a magnet and curve around to enter the south pole.

In physical terms, a magnetic field is defined by vectors that represent both its strength and direction, quantitatively described by the unit 'tesla'. When a magnetic field comes in contact with ferromagnetic materials, it influences the alignment of their magnetic domains, which can lead to the creation of a permanent magnet if the material's domains align uniformly in the direction of the field. Understanding this invisible but powerful force is fundamental in the studies of not only physical chemistry but also in various applications such as electric motors, generators, and magnetic resonance imaging.

Magnetic Domains

Magnetic domains are essentially small regions within ferromagnetic materials where the magnetic moments of atoms are aligned in the same direction. Think of these domains like tiny magnets within a larger piece of material. Each domain is magnetized to its full potential, but in the unmagnetized material, these domains are randomly oriented which results in the overall magnetic fields canceling each other out.

When an external magnetic field is applied to a ferromagnetic material, the energy of the magnetic field works to reorient these domains. As the domains become aligned, they combine to create a stronger, large-scale magnetic field, contributing to the magnetization of the entire material. This alignment process is responsible for the ferromagnetic substance's transformation into a permanent magnet upon exposure to a magnetic field. This concept is a key topic in the study of magnetism and has wide-ranging applications, from data storage (in the form of hard drives) to the generation of electricity.

Permanent Magnet

A permanent magnet is an object that maintains a persistent magnetic field around it without the need for external energy. These materials, such as iron, cobalt, and nickel, become permanent magnets once their magnetic domains are uniformly aligned in the presence of a strong magnetic field. Once all the domains are oriented in the same direction, the object exhibits a continuous external magnetic field, thus becoming a permanent magnet.

This effect is not just temporary. Even after the external magnetic field is removed, the domains remain aligned due to the domains' energy being minimized in this configuration, making the alignment stable. As such, permanent magnets are key components in a multitude of devices and are used to convert mechanical energy into magnetic energy and vice versa. These permanent magnets can lose their magnetization if heated to a high temperature, known as the Curie temperature, exposed to a strong opposing magnetic field, or through physical jarring or damage, which can cause the domains to lose their uniform alignment.

Physical Chemistry

Physical chemistry is the branch of science that deals with the study of how matter behaves on a molecular and atomic level and how chemical reactions occur. It combines principles of physics and chemistry to understand the physical properties of molecules, the forces that act upon them, and the interactions between them. Within this realm, magnetism is a fundamental property that physical chemists study to comprehend the behavior of materials and their responses to magnetic fields.

Exploring magnetic phenomena such as ferromagnetism, diamagnetism, and paramagnetism allows chemists to develop new materials and technologies. It also helps in elucidating the underlying principles of various technologies, such as semiconductor devices and spectroscopy techniques. The study of magnetic fields, domains, and permanent magnets is interlaced with physical chemistry's goal to explain observable macroscopic properties of materials based on their microscopic interactions.