MCQ Detailed View

Lubricants are substances that reduce friction between two surfaces in contact, allowing them to move smoothly over each other. Among the options given, graphite is widely used as a solid lubricant because of its unique physical and chemical properties.

Graphite is a form of carbon with a layered structure. Each layer is made up of carbon atoms arranged in hexagonal sheets. These layers can easily slide over each other due to weak forces holding them together, which makes graphite an excellent lubricant. Because of this property, graphite reduces wear and tear in machines and tools where liquid lubricants are unsuitable, especially in high-temperature or dusty environments.

Silica, iron oxide, and diamond do not serve as lubricants. Silica is commonly found in sand and is abrasive rather than slippery. Iron oxide is a rust compound and can cause damage to surfaces, while diamond is extremely hard and is used as a cutting or polishing material, not as a lubricant.

Graphite is commonly used in locks, hinges, and heavy machinery. It works effectively even in harsh conditions, such as in space equipment and industrial machines, where liquid lubricants might evaporate or break down.

Understanding the role of graphite as a lubricant is important in physics and engineering. It demonstrates how the microscopic structure of materials can affect their macroscopic properties and practical uses.