Which factor has little effect on colloidal particles due to their small size?

Colloidal particles are extremely small, typically in the range of 1 nanometer to 1 micron. Because of their tiny size, gravity has a minimal effect on them compared to larger particles. In fluid systems, gravitational forces tend to impact larger particles, causing them to settle out of solution more readily. However, colloids remain suspended due to a combination of their small size and the Brownian motion caused by collisions with surrounding fluid molecules, which counteracts the gravitational pull.

The other factors listed—electromagnetic forces, temperature variations, and electrical conductivity—are all significant in influencing colloidal stability and behavior. Electromagnetic forces can interact with colloidal particles based on their charge and surface properties. Temperature variations can affect the kinetic energy of the particles, influencing their movement and stability. Electrical conductivity relates to the ionic content of the solution, which can affect the repulsive or attractive forces acting on colloids. Given these influences, gravity stands out as having little effect on colloidal particles due to their small scale.