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In a multiple-choice question, the four options give you a safety net: a wildly wrong answer usually does not appear among them. JEE Main's numerical-value questions take that net away. You type a number, and either it is right or it is not. This post explains how these questions work, shows three traps with worked examples, and gives a weekly routine for physics.
How does Section B work in JEE Main?
According to the JEE (Main) 2026 Information Bulletin, Paper 1 (B.E./B.Tech.) has 75 questions for 300 marks in 3 hours. Mathematics, Physics and Chemistry each have 20 multiple-choice questions in Section A and 5 questions in Section B whose answers are filled in as a numerical value, for 100 marks per subject.
The bulletin's marking rules for Section B are:
Correct answer: +4.
Incorrect answer: −1.
Unanswered or marked for review without a value: 0.
If a question is found to be incorrect or is dropped, all candidates in that shift get +4.
It also says the answer should be rounded off to the nearest integer, entered with the on-screen keypad, and that candidates should do calculations with the constants given in the question, if any. So in physics, Section B is worth 20 marks, and every question in it counts. Check the bulletin for your own exam year, because NTA publishes a new one each cycle. Our post on JEE Main's two sessions covers the rest of the exam calendar.
Why do numerical questions feel harder than MCQs?
Without options you cannot work backwards or eliminate. You also cannot spot a slip by noticing that your answer is not on the list. Because a wrong answer costs a mark, a guess is a real risk. Our post on negative marking works through when guessing pays. For a typed number with no options, the chance of a lucky guess is very small, so attempt a question only when you have worked it out.
The good news is that most mistakes in this section are not about physics. They are about rounding, constants and units. Those can be trained.
Trap 1: using your own value of a constant
A ball is projected at 25 m/s at 45° to the horizontal. Find its range in metres, taking g = 9.8 m/s².
R = u² sin 2θ / g. With θ = 45°, sin 90° = 1.
R = 25² / 9.8 = 625 / 9.8 = 63.78 m.
Rounded to the nearest integer: 64.
If you use g = 10 out of habit, you get 625 / 10 = 62.5, which rounds to 62 or 63, not 64. One habit changes the integer. The bulletin's own advice is to use the constants given. For harder projectile set-ups, see our post on projectiles on an incline.
Trap 2: the unit asked for
A 5 μF capacitor is charged to 100 V. Find the energy stored, in mJ.
U = ½CV² = ½ × (5 × 10⁻⁶) × (100)².
U = ½ × 5 × 10⁻⁶ × 10⁴ = 0.025 J.
In millijoules: 0.025 J × 1000 = 25 mJ. Answer: 25.
If you stop at 0.025 and round, you type 0, which is marked wrong. Underline the unit in the question before you start. More practice is in our guide to capacitor problems.
Trap 3: the relation hidden in "stretched"
A wire of resistance 12 Ω is stretched uniformly to twice its length. Find its new resistance in ohms.
R = ρL/A. Stretching keeps the volume the same, so L × A is constant.
If L doubles, A halves. So R becomes ρ(2L)/(A/2) = 4ρL/A.
New R = 4 × 12 = 48 Ω. Answer: 48.
The common wrong answer is 24, from doubling the length and forgetting the area. In numericals, a single word like "stretched", "isolated" or "smooth" carries a whole equation.
How should you round, and when?
Carry full precision through every step and round once, at the end. If you round 9.8 to 10, or √3 to 2, mid-way, small errors add up and can cross a .5 boundary. If your final answer is far from an integer, for example 37.4 when the question looks designed for a whole number, re-check the set-up before you enter anything.
A weekly routine for physics numericals
Research supports two ideas behind this plan. In a study of 126 seventh-grade students, Rohrer, Dedrick and Stershic found that mixing problem types in practice, rather than doing one type at a time, gave higher scores on tests one day and 30 days later. And Roediger and Karpicke found that taking tests improved retention a week later more than restudying the same material did.
Monday and Thursday: mixed sets. Ten numerical-value problems from at least four units of the JEE (Main) 2026 physics syllabus, shuffled, with no options. Thirty minutes.
Tuesday: precision drill. Five problems where you write every intermediate value to three significant figures and round only at the end.
Wednesday: error log. Sort every wrong answer from the week as constant, unit, rounding, set-up or concept.
Friday: timed Section B. Five questions in 15 minutes, as in a real paper.
Weekend: fix the top error type. If units cost you most, write the unit after every line of working for a week.
When the set-up is the problem rather than the arithmetic, the Fermi Problem Library has worked problems with a step-by-step solver that explains the reasoning rather than printing an answer.
Start with tonight's set: three problems from three different chapters, solved to full precision and rounded only at the last line.
