JEE Main Physics Experimental Skills 2027: Vernier, Screw Gauge & All 18 Experiments

This is the unit most students skip because it feels like a lab manual. That is a mistake. The NTA syllabus lists 18 specific experiments, and questions come straight from them: reading a vernier, spotting a zero error, or finding g from a graph slope.

Experimental questions reward exactly one habit: reading instruments carefully.

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Chapter at a Glance

Priority reflects past-paper trends, not an official NTA weightage.

What the NTA Syllabus Covers

• Familiarity with the approach and observations of 18 listed experiments and activities
• Instruments: vernier calipers, screw gauge, metre scale and related setups
• Mechanics experiments: pendulum, Young's modulus, surface tension, viscosity, speed of sound, specific heat
• Electricity and optics: resistivity by metre bridge, Ohm's law, galvanometer, focal length, prism, refractive index, diode characteristics

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Master These Topics

1. The 18 Experiments at a Glance

2. Vernier Calipers and Screw Gauge

Vernier caliper: least count = 1 MSD − 1 VSD. If 10 VSD equal 9 MSD with 1 MSD = 1 mm, the least count is 0.1 mm. Reading = MSR + (VSR × LC) − zero error.

Worked example: MSR = 24 mm, the 6th vernier division coincides, LC = 0.1 mm. Reading = 24 + 0.6 = 24.6 mm.

Screw gauge: least count = pitch / number of circular divisions. With pitch 1 mm and 100 divisions, LC = 0.01 mm.

Worked example: MSR = 3 mm, circular scale reading = 47, zero error = +0.03 mm. Observed = 3 + 0.47 = 3.47 mm, so corrected = 3.47 − 0.03 = 3.44 mm.

Trap: Positive zero error is subtracted from the reading, and negative zero error is added. Read the sign carefully.

3. Simple Pendulum and Graph Slopes

Since T² = 4π²l / g, a graph of T² against l is a straight line with slope 4π²/g. If the slope is 4 s²/m, then g = 4π²/4 = π² ≈ 9.87 m/s².

4. Meter Bridge and Half-Deflection Method

Meter bridge: X = R (100 − l)/l, and resistivity follows from ρ = XA / L.

Half-deflection method for galvanometer resistance: G = RS / (R − S), where R is the series resistance and S the shunt that halves the deflection.

Worked example: R = 2000 Ω and S = 100 Ω give G = 2000 × 100 / 1900 ≈ 105 Ω.

5. Error Sources to Recognise

• Parallax and zero error in instruments.
• Heat loss in calorimetry (method of mixtures).
• End correction in resonance tube: the antinode forms slightly above the open end.

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Common Traps to Avoid

• Adding positive zero error instead of subtracting it.
• Forgetting the end correction when computing the speed of sound with a resonance tube.
• Reading slope of a T² versus l graph wrongly by mixing up axes.
• Ignoring parallax when reading scales in optics experiments.

60-Second Revision Sheet

• Vernier LC = 1 MSD − 1 VSD; screw gauge LC = pitch/divisions
• Corrected reading = observed − zero error (with sign)
• Pendulum: slope of T² versus l is 4π²/g
• Half-deflection G = RS/(R − S); meter bridge X = R(100 − l)/l

Your Study Plan

1. Day 1: vernier and screw gauge readings with zero error, twenty examples.
2. Day 2: pendulum, Young's modulus, surface tension and viscosity experiments.
3. Day 3: electricity experiments: meter bridge, Ohm's law, galvanometer.
4. Day 4: optics and diode experiments, then a timed set.

Practice Experimental Skills Questions Free → (opens in a new tab)

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Continue Your Physics Journey

• Previous chapter: Electronic Devices
• All 20 JEE Main Physics chapters
• Complete JEE Main Syllabus 2027 guide

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