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Exam level1 past question

Ohm's Law and Basic Electrical Quantities

Understand Ohm's law, current, voltage, resistance, conductance, and how they relate in electrical circuits.

Why this shows up in the exam

NEET tests your ability to apply Ohm's law and calculate basic electrical quantities in various situations.

How NEET tests this

Direct recallNumerical

Learn the idea

Ohm’s law states V = I R, linking voltage, current and resistance. The reciprocal of resistance is called conductance (G) and equals I⁄V, measured in siemens. Recognising that G = 1⁄R instantly unlocks many NEET problems.

🧠 Memory hook: Think of G as the ‘good’ opposite of R – Goodness = 1⁄Resistance!

Get this one clearly and it pays off every single time it shows up in the paper. 🎯

Formulas & facts to keep ready

  • V = I R (Ohm’s law)
  • R = V⁄I
  • G = 1⁄R (conductance)
  • Unit of conductance = siemens (S)
  • σ = G·(l⁄A) (conductivity relates to conductance by geometry)
  • Resistance depends on resistivity ρ: R = ρ l⁄A

How to approach it

  1. 1Read the question and note which quantity (V, I, R or G) is required
  2. 2Write the appropriate relation – V = I R or G = 1⁄R – using symbols given
  3. 3Substitute known values and solve algebraically
  4. 4Check the unit (Ω for R, S for G) to confirm the answer

Worked example — watch it click

The reciprocal of resistance is:

  • A)reactance
  • B)mobility
  • C)conductivity
  • ✅conductance

The concept behind this problem

The question asks directly for the quantity that is the reciprocal of resistance, testing whether you know that conductance G = 1⁄R, not conductivity or reactance.

Step by step

  1. 1Resistance R is defined by Ohm’s law as R = V⁄I.
  2. 2Taking the reciprocal gives 1⁄R = I⁄V.
  3. 3The quantity defined as conductance G equals I⁄V, measured in siemens, so G = 1⁄R.
  4. 4Reactance is the AC opposition due to inductance or capacitance, not the reciprocal of R.
  5. 5Mobility describes carrier drift per electric field, and conductivity is a material constant (σ) related to conductance by geometry, not the direct reciprocal of a resistor.
  6. 6So the correct answer is conductance.

Watch out

Students often pick conductivity because it sounds similar, overlooking that only conductance is defined as the direct reciprocal of resistance.

Common slip-ups that cost marks

  • •Confusing conductance (1⁄R) with conductivity (σ), which involves material dimensions
  • •Choosing reactance for AC problems when the question is purely resistive
  • •Forgetting that conductance is the reciprocal, not the square or any other function

🌟 That's the whole idea — you've got this. Try the practice set below; every question you attempt makes it stick a little harder.

Practise it

These are real questions from past NEET papers that test this exact idea.

Question 1 of 1

The reciprocal of resistance is:

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