Capillary Rise Formula — the NEET Physics formula with its derivation, variables, validity constraints and worked solver.
Capillary Rise Formula Valid for static liquids in narrow cylindrical tubes where the meniscus is spherical and gravitational effects on the meniscus shape are negligible compared to surface tension. Identify the upward force due to surface tension: F up = 2 pi r sigma cos(theta). Identify the downward force due to the weight of the liquid column: F down = m g = (rho pi r 2 h) g. Apply equilibrium condition: F up = F down. Solve for height h: h = (2 sigma cos(theta)) / (rho g r). The radius of the tube must be small (capillary scale). The liquid must be in static equilibrium. Assumes a constant contact angle. Viscosity is not a factor in the static height. Believing that a wider tube results in a higher rise (actually, height is inversely proportional to radius). Ignoring the contact angle (assuming it is always zero/wetting). Thinking the formula applies to dynamic flow rather than static equilibrium.