Final answer:
The equipment used to separate plasma or serum from red blood cells is a centrifuge, which operates using centrifugal force to separate components of blood by density.
Step-by-step explanation:
A centrifuge is a device that operates on the principle of centrifugal force to separate components of different densities. When a blood sample is placed in a centrifuge and spun at high speeds (often 3000 rpm or higher), the denser components, such as red blood cells and platelets, move outward and settle at the bottom, forming a layer called the pellet. The less dense component, the plasma or serum, remains as the upper liquid layer.
Plasma contains about 90 percent water and is rich in proteins, coagulation factors, and antibodies which are essential for the body's defense and homeostasis. Centrifugation is vital for various medical tests, including a hematocrit, which measures the percentage of red blood cells (erythrocytes) in a blood sample, and for preparing samples for further analysis, such as in the study of macromolecules like DNA and proteins.