In a viscosity-flow experiment, which observation would indicate that viscosity has increased?

In a viscosity-flow experiment, which observation would indicate that viscosity has increased?

• A. Flow rate increases
• B. Flow rate decreases
• C. Flow rate remains the same
• D. Flow rate becomes erratic

Answer: (B)

Higher viscosity means the fluid resists movement more, so under the same driving force it flows more slowly. In a fixed setup (same pressure difference, same tube, same temperature), increasing viscosity reduces the volumetric flow rate, which is described by the relation Q ∝ 1/μ from Poiseuille’s law. So seeing the flow rate decrease is the clear sign that viscosity has gone up. If the flow rate increased, viscosity would have decreased; if it stayed the same, viscosity didn’t change; erratic flow suggests non-Newtonian effects or measurement issues.

Higher viscosity means the fluid resists movement more, so under the same driving force it flows more slowly. In a fixed setup (same pressure difference, same tube, same temperature), increasing viscosity reduces the volumetric flow rate, which is described by the relation Q ∝ 1/μ from Poiseuille’s law. So seeing the flow rate decrease is the clear sign that viscosity has gone up. If the flow rate increased, viscosity would have decreased; if it stayed the same, viscosity didn’t change; erratic flow suggests non-Newtonian effects or measurement issues.