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Experimental Skills formula sheet

Every formula in the Experimental Skills chapter for JEE Main, with one line on when it applies. Topic 1 is open to everyone; sign in free to read all 26 and download the PDF.

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How we count: 7× asked means 7 past JEE Main questions in the PrepWiser bank needed that formula, and "last" is the latest year one appeared. ★ marks formulas asked 8 or more times.

Measuring instruments

Vernier callipers
13× asked, last 2026
LC=1 MSD−1 VSD=MSDNreading=MSR+n×LC\begin{aligned}&\text{LC}=1\,\text{MSD}-1\,\text{VSD}=\frac{\text{MSD}}N\\&\text{reading}=\text{MSR}+n\times\text{LC}\end{aligned}
NN VSD =(N−1)=(N-1) MSD. NN VSD =M=M MSD: LC =∣1−M/N∣=|1-M/N| MSD. Convert MSD first.
Extended vernier
N VSD=(kN±1) MSD ⇒ LC=MSDNN\ \text{VSD}=(kN\pm1)\ \text{MSD}\ \Rightarrow\ \text{LC}=\frac{\text{MSD}}N
k≥2k\ge2. E.g. 10 VSD = 19 MSD: LC = 0.1 MSD.
Vernier zero error
11× asked, last 2026
true=observed−e,e+=+n×LC\text{true}=\text{observed}-e,\qquad e_+=+n\times\text{LC}
Zero right of main zero: ++. Left: e=−(N−n)×e=-(N-n)\timesLC (some keys use −n×-n\timesLC).
Screw gauge
9× asked, last 2026
pitch=distancerotations,LC=pitchNcircular\text{pitch}=\frac{\text{distance}}{\text{rotations}},\qquad \text{LC}=\frac{\text{pitch}}{N_{\text{circular}}}
Reading = MSR + CSR × LC. Turn one way only (backlash).
Screw gauge zero error
12× asked, last 2026
d=MSR+CSR×LC−ed=\text{MSR}+\text{CSR}\times\text{LC}-e
Circular zero nn below the line: e=+ne=+n LC; above: −n-n LC.
Spherometer
R=l26h+h2R=\frac{l^2}{6h}+\frac h2
ll = leg spacing, hh = height. Also thickness of thin plates.

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20 more formulas in 5 topics

Mechanics and properties of matter, Heat and sound, Electricity, Optics and Semiconductor devices. Read the first part free. Sign in free with Google to read the rest and download the PDF.

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Mechanics and properties of matter

  • Simple pendulum: gg1×
  • Damped pendulum
  • Metre scale: moments
  • Young's modulus (Searle)
  • Surface tension by capillary rise
  • Viscosity by terminal velocity

Heat and sound

  • Speed of sound: resonance tube
  • Specific heat: method of mixtures

Electricity

  • Metre bridge1×
  • End correction (metre bridge)
  • Resistance by Ohm's law
  • Galvanometer: half deflection2×

Optics

  • u–v method4×
  • Error in focal length3×
  • Convex mirror with a convex lens
  • Prism: deviation vs incidence
  • Glass slab: travelling microscope6×

Semiconductor devices

  • Diode I–V curve
  • Zener regulator
  • Multimeter checks1×

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About 60 past JEE Main questions from this chapter, with instant answer checking and step-by-step solutions where available. Free, and you can start without signing up.

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Version 1, October 2026. Free to share for study, as it is. Please don't sell it or remove the PrepWiser name.

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