MCQ Detailed View

Surface tension is a property of liquids that allows them to resist an external force due to cohesive forces between molecules. It is commonly observed in phenomena such as water droplets forming spheres or insects walking on water. Surface tension is defined as the force acting along the surface of a liquid per unit length.

The unit of surface tension depends on the system of measurement being used. In the CGS (centimeter-gram-second) system, the unit of force is the dyne and the unit of length is the centimeter. Therefore, surface tension is measured in dyn/cm (dyne per centimeter) in the CGS system.

Other options listed, such as Pascal, which is a unit of pressure, and N/m (Newton per meter), which is the SI unit of surface tension, are not correct for CGS measurements. One dyn/cm is equivalent to 0.001 N/m in the SI system.

Surface tension arises due to the cohesive forces between liquid molecules. Molecules at the surface experience an imbalance of forces since there are no molecules above them. This imbalance creates a net inward force that minimizes the surface area of the liquid, which is why water forms spherical droplets.

Understanding the unit of surface tension is important in physics and everyday science. It helps explain the behavior of liquids, phenomena like capillarity, the formation of bubbles, and practical applications in detergents, paints, and biological membranes.

By knowing that dyn/cm is the CGS unit, students can correctly convert surface tension values between different systems and solve physics problems involving liquids and interfaces.