NEET Experimental Skills PYQs | 2013–2025

Experimental Skills — Solutions (2025 → 2013)

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2025

Q1. Focal length of convex lens:

• Lens formula: $\frac{1}{f} = \frac{1}{v} – \frac{1}{u}$f1​=v1​−u1​
• Measure object distance $u$u and image distance $v$v.
• Calculate $f$f. Average over multiple trials.

Q2. Verification of Ohm’s law:

• Connect a resistor in series with a battery and ammeter.
• Measure current $I$I for different applied voltages $V$V.
• Plot $V$V vs $I$I. Straight line → Ohm’s law verified.

Q3. Specific heat capacity (method of mixtures):

• Mix heated solid with water in calorimeter.
• Measure initial and final temperatures.

$$m_s c_s (T_s – T_f) = m_w c_w (T_f – T_w)$$ms​cs​(Ts​−Tf​)=mw​cw​(Tf​−Tw​)

• Solve for $c_s$cs​.

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2024

Q1. Resistivity using meter bridge:$$\rho = \frac{R}{L} \cdot \frac{A}{L’}$$ρ=LR​⋅L′A​

• Balance the bridge using galvanometer, measure lengths $l_1$l1​, $l_2$l2​.

Q2. Internal resistance using potentiometer:$$r = \frac{V – V_{AB}}{I}$$r=IV−VAB​​

• Connect cell, adjust potentiometer for zero deflection → measure balancing length.

Q3. Acceleration due to gravity using simple pendulum:$$T = 2 \pi \sqrt{\frac{l}{g}} \implies g = \frac{4 \pi^2 l}{T^2}$$T=2πgl​​⟹g=T24π2l​

• Measure $l$l and $T$T → calculate $g$g.

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2023

Q1. Wavelength using diffraction grating:$$\lambda = \frac{d \sin \theta}{n}$$λ=ndsinθ​

• Measure diffraction angle $\theta$θ, grating spacing $d$d, order $n$n.

Q2. e/m ratio using Thomson’s method:$$\frac{e}{m} = \frac{2V}{B^2 r^2}$$me​=B2r22V​

• Measure radius $r$r of electron path, voltage $V$V, magnetic field $B$B.

Q3. Conservation of energy:

• Using pendulum: maximum potential energy = maximum kinetic energy → measure heights and velocity.

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2022

Q1. Refractive index using travelling microscope:$$\mu = \frac{\text{real thickness}}{\text{apparent thickness}}$$μ=apparent thicknessreal thickness​

• Measure apparent shift using microscope, compare with real thickness.

Q2. Coefficient of viscosity using Stoke’s method:$$\eta = \frac{2}{9} \frac{r^2 g (\rho_s – \rho_l)}{v}$$η=92​vr2g(ρs​−ρl​)​

• Drop spheres in liquid, measure terminal velocity $v$v, calculate $\eta$η.

Q3. Focal length of concave mirror (distant object):

• Use distant object → parallel rays focus at principal focus.
• Measure distance from mirror → focal length.

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2021

Q1. Focal length of lens combination:

• Use lens formula for each lens, combine:

$$\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2} – \frac{d}{f_1 f_2}$$F1​=f1​1​+f2​1​−f1​f2​d​

Q2. Surface tension using capillary rise:$$T = \frac{h \rho g r}{2}$$T=2hρgr​

• Measure capillary rise $h$h, radius $r$r, liquid density $\rho$ρ.

Q3. Modulus of rigidity using torsional pendulum:$$T = 2 \pi \sqrt{\frac{I}{C}} \implies C = \frac{4 \pi^2 I}{T^2}$$T=2πCI​​⟹C=T24π2I​

• Measure period $T$T, moment of inertia $I$I → calculate rigidity $C$C.

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2020

Q1. Specific resistance using Carey Foster bridge:$$\rho = k \frac{l_1 – l_2}{l}$$ρ=kll1​−l2​​

• Measure bridge balance lengths → calculate $\rho$ρ.

Q2. Velocity of sound using resonance tube:$$v = 4 L f$$v=4Lf

• Adjust water level until resonance, measure length $L$L, known frequency $f$f.

Q3. Energy stored in spring (Hooke’s law):$$E = \frac{1}{2} k x^2$$E=21​kx2

• Measure extension $x$x for known force → determine k → calculate energy.

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2019

Q1. Wavelength using Newton’s rings:$$\lambda = \frac{D_{n+p}^2 – D_n^2}{4pR}$$λ=4pRDn+p2​−Dn2​​

• Measure diameters of rings $D_n$Dn​, radius of curvature $R$R.

Q2. Frequency of AC mains using sonometer:

• Adjust sonometer wire → produce stationary waves → frequency = n × (wave speed / 2L)

Q3. Laws of reflection/refraction:

• Measure incident and reflected/refracted angles → verify: $i = r$i=r, $n = \sin i / \sin r$n=sini/sinr

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2018

Q1. Resistivity using metre bridge: same as 2024 Q1.

Q2. Coefficient of linear expansion:$$\alpha = \frac{\Delta L}{L \Delta T}$$α=LΔTΔL​

• Measure initial length, change in length, temperature difference.

Q3. Acceleration due to gravity using free-fall:$$g = \frac{2s}{t^2}$$g=t22s​

• Measure distance $s$s and fall time $t$t.

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2017

Q1. Focal length of concave lens:

• Combine with convex lens → measure image distance → apply lens formula.

Q2. Ohm’s law: same as 2025 Q2.

Q3. Work function using photoelectric effect:$$\phi = h\nu – eV_s$$ϕ=hν−eVs​

• Measure stopping potential $V_s$Vs​ for known light frequency $\nu$ν.

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2016

Q1. Focal length using u–v method: $f = \frac{uv}{u+v}$f=u+vuv​

• Measure object distance $u$u, image distance $v$v.

Q2. Internal resistance using potentiometer: same as 2024 Q2.

Q3. Modulus of elasticity using Searle’s apparatus:

• Measure extension under known load → calculate Young’s modulus:

$$Y = \frac{F L}{A \Delta L}$$Y=AΔLFL​

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2015

Q1. Refractive index of liquid using convex lens:$$\mu = \frac{f_{\text{air}}}{f_{\text{liquid}}}$$μ=fliquid​fair​​

Q2. Resistance using Wheatstone bridge: $R = \frac{l_1}{l_2} R_2$R=l2​l1​​R2​

Q3. Moment of inertia of flywheel: $I = \frac{\tau}{\alpha}$I=ατ​

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2014

Q1. Focal length by lens displacement:$$f = \frac{L^2 – d^2}{4L}$$f=4LL2−d2​

• L = distance between object and screen, d = displacement of lens.

Q2. Ohm’s law verification: V vs I for series and parallel resistors.

Q3. Coefficient of viscosity: same as 2022 Q2.

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2013

Q1. Focal length of concave mirror: measure distance from distant object to mirror.

Q2. Conservation of energy: PE at height = KE at bottom → measure velocity/height.

Q3. Specific heat capacity using calorimeter:$$m c (T_{final} – T_{initial}) = m_w c_w (T_w – T_{final})$$mc(Tfinal​−Tinitial​)=mw​cw​(Tw​−Tfinal​)