Experimental Physics in NEET 2026 covers 18 distinct experiments spanning measurement instruments, classical mechanics, wave optics, thermal physics, electricity, optics, and semiconductor electronics. Mastery of these experiments — particularly instrument readings, error analysis, and graph interpretation — reliably secures 1–2 marks per year in the examination.

Measurement Instruments form the bedrock of all experimental work. The Vernier caliper measures external diameter, internal diameter, and depth. Its least count is LC = 1 MSD − 1 VSD; for a standard caliper with 50 VSD = 49 MSD and 1 MSD = 1 mm, LC = 0.02 mm. The reading formula is: Reading = MSR + (coinciding VSD × LC). Zero error is critical: a positive zero error (Vernier zero to the right of main scale zero) means the instrument reads MORE than the actual value — the correction is to subtract the zero error from the raw reading. A negative zero error (Vernier zero to the left) means the instrument reads LESS — add the zero error. The mnemonic "PS-NA" (Positive-Subtract, Negative-Add) encodes this rule. The screw gauge provides even higher precision (LC = pitch/divisions = 0.5/50 = 0.01 mm) and measures wire diameter and thin sheet thickness. Backlash error in the screw gauge arises from reversing the direction of thimble rotation; it is prevented by always rotating in one direction only. Both instruments have dimensional formula [L] and SI unit metres.

Mechanics Experiments cover five major phenomena. The simple pendulum gives T = 2π√(l/g); plotting $T^{2}$ vs l yields a straight line through the origin with slope = 4π^{2}/g, from which g can be determined experimentally. Crucially, the effective length l = string length + bob radius; neglecting the bob radius leads to a systematic underestimation of g. Young's modulus is measured by Searle's apparatus: Y = FL/(A$\Delta L$) in units of Pa, where the stress-strain graph's slope in the linear region gives Y. Surface tension by capillary rise: S = hrρg/(2cosθ) — for water-glass, θ = 0°, simplifying to S = hrρg/2. Viscosity by Stokes' law at terminal velocity: v_t = 2$r^{2}$(ρ−σ)g/(9η), where at terminal velocity, weight = buoyancy + Stokes drag (6πηrv_t). The principle of moments (metre scale) gives the balance condition m_{1}l_{1} = m_{2}l_{2}.

Waves and Thermal Experiments include the resonance tube and method of mixtures. The resonance tube is the most frequently tested waves experiment. First resonance occurs at air column length l_{1} + e = λ/4 and second resonance at l_{2} + e = 3λ/4, where e is the end correction. The preferred speed-of-sound formula is v = 2f(l_{2} − l_{1}) because the end correction cancels algebraically when the two resonance lengths are subtracted. Using v = 4fl_{1} alone is less accurate because it includes the end correction: effectively v = 4f(l_{1} + e). The end correction itself can be found: e = (l_{2} − 3l_{1})/2. In specific heat measurement by the method of mixtures, the heat equation m_{1}c_{1}($T_{1}$ − T) = m_{2}c_{2}(T − $T_{2}$) + m_cal c_cal(T − $T_{2}$) must include the calorimeter's heat capacity; omitting it gives an overestimate of c_{2}.

Electrical Experiments cover four instruments. The metre bridge uses the Wheatstone bridge principle: at balance, R/S = l/(100 − l). Interchanging R and S shifts the balance point to l' = 100 − l (a useful self-consistency check). Resistivity: ρ = RA/L where A = π$d^{2}$/4 (measured by screw gauge). The galvanometer resistance is found by the half-deflection method: G ≈ S when S << R, and the figure of merit k = I/θ (A/div) quantifies sensitivity. Ohm's law verification gives a straight V-I graph (slope = R) for ohmic conductors; non-ohmic devices (diodes, filament bulbs) give curved graphs.

Optics Experiments require strict adherence to Cartesian sign convention. For a concave mirror (f < 0), the u-v method gives 1/v + 1/u = 1/f; a 1/v vs 1/u graph has intercepts at ±1/f. For a convex lens (f > 0), the lens formula is 1/v − 1/u = 1/f. A convex mirror (f > 0) requires an auxiliary convex lens because its virtual images cannot be projected on a screen. The prism experiment measures refractive index using μ = sin((A + δ_min)/2)/sin(A/2) at the condition of minimum deviation (i = e), where the i-delta graph is U-shaped. The glass slab experiment uses μ = real depth/apparent depth, measured with a travelling microscope.

Electronics Experiments focus on semiconductor I-V characteristics. The p-n junction diode shows exponential current rise in forward bias after the threshold voltage: ~0.7 V for Si and ~0.3 V for Ge (Si has wider band gap ~1.1 eV vs Ge ~0.67 eV). In reverse bias, a small saturation current flows until breakdown. The Zener diode shows sharp reverse breakdown at V_Z with nearly constant voltage — it is used as a voltage regulator and always requires a series current-limiting resistor. LEDs emit light in forward bias with V_th ≈ 1.5–3 V (higher band gap materials emit higher-energy/shorter-wavelength photons). Resistor identification uses the color code BBROYGBVGW = 0–9.

The most heavily tested topics in NEET are: (1) Vernier/screw gauge reading with zero error correction, (2) resonance tube speed calculation and end correction, (3) metre bridge balance and resistivity, (4) graph interpretation ($T^{2}$ vs l, V-I, i-delta, 1/v vs 1/u), and (5) semiconductor threshold voltages. Drilling the key formulas and understanding the error corrections for each instrument are essential for scoring full marks on experimental physics questions.