Problem 81 - A Complete Resource Book in Chemistry for JEE Main

Question

Which of the following alloy is used for making magnets for hearing aids? (a) invar (b) german silver (c) monel metal (d) alnico

Step-by-Step Solution

Answer

The alloy used for making magnets in hearing aids is alnico.

Step 1: Identify Alloy with Magnetic Properties

Examine the list of alloys to identify which one is known for its magnetic properties. In general, magnets are made from materials that can maintain a magnetic field.

Step 2: Consider Alnico

Alnico is well known for its capability to retain a strong magnetic field. It is commonly used in applications where permanent magnets are required, including hearing aids.

Step 3: Review the Other Alloys

Check the other options: Invar is known for its low thermal expansion, german silver is known for its corrosion resistance, and monel metal is known for its strength and corrosion resistance, but none are particularly noted for magnetic properties.

Step 4: Conclusion on Suitable Alloy

Given the options and their properties, alnico is the only alloy among them known specifically for its strong magnetic properties, making it suitable for use in hearing aids.

Key Concepts

Magnetic Properties

Magnetic properties refer to the ability of materials to either attract or repel one another based on their magnetic fields. These properties are essential in determining how a material will respond when exposed to a magnetic field or when it acts as a magnet itself. Typically, materials that exhibit strong magnetic properties are made from ferromagnetic materials, such as iron, cobalt, or nickel.

Alnico is an alloy that stands out for its excellent magnetic properties. It consists mainly of aluminum (Al), nickel (Ni), cobalt (Co), with small amounts of other elements like iron and copper. The significance of these elements is that they endow Alnico with a strong magnetic field, making it an ideal choice for various applications, such as in motors, sensors, and of course, hearing aids.

When making magnets, choosing a material with enduring magnetic properties is crucial, as it will maintain a magnetic field over time without the need for continuous electrical power. Alnico retains its magnetism effectively, making it a preferred choice for permanent magnets.

Hearing Aids

Hearing aids are small electronic devices designed to improve hearing by amplifying sound. They are especially crucial for individuals with hearing impairments to better perceive sounds in their environment, facilitating improved communication and quality of life.

Key components of hearing aids include:

• Microphone: Captures sound from the environment.
• Amplifier: Increases the strength of the sound signals.
• Speaker: Transmits the amplified sounds to the ear.
• Battery: Powers the device components.

Permanent magnets, like those made from alnico, are instrumental in hearing aids. These magnets are utilized in miniaturized speaker systems within the devices. They effectively convert the amplified electrical signals back into sound waves that the user can hear. The durable magnetic properties of alnico ensure the fidelity and clarity of sound transmission in hearing aids, making communication more accessible for users.

Alloys

Alloys are materials composed of two or more elements, with at least one being metallic. They are specifically engineered to enhance the properties of the base metal, such as strength, corrosion resistance, or magnetic properties.

Alnico is an example of an alloy that is tailored to meet specific needs in technological and industrial applications. It combines aluminum, nickel, and cobalt to create a highly magnetic material. Each component in alnico plays a strategic role:

• Aluminum contributes to structural integrity and machinability.
• Nickel enhances magnetic strength and corrosion resistance.
• Cobalt is pivotal for improving heat resistance and magnetic retention.

The intentional combination of these elements allows alnico to fulfill stringent requirements for permanent magnets used in various devices, including hearing aids. Alloys like alnico are vital due to their customizable attributes, which allow them to be fine-tuned for optimal performance in specific environments.