The IISER Aptitude Test (IAT) 2026 will be held on June 7, 2026, in online/CBT mode at multiple exam centres across the country to assess candidates’ domain knowledge in Physics, Chemistry, Mathematics, and Biology.
Only a few days are left for the examination, and candidates’ IAT 2026 preparation must now be in the final stage of revision. Since Physics is considered one of the most challenging subjects, revising the subject requires significant effort and focused practice.
To support candidates in their preparation, SciAstra is presenting the IAT 2026 Physics Most Important Questions based on previous year trends, NCERT concepts, and expert analysis of high-weightage topics.
These questions are carefully designed to test conceptual understanding, analytical thinking, and problem-solving skills required for the examination.
The question set covers major Physics topics such as Mechanics, Thermodynamics, Electrodynamics, Current Electricity, Modern Physics, Optics, Waves & Oscillations, Magnetism, and Semiconductors. Practising these important questions will help students improve speed, accuracy, and confidence while revising the most frequently asked concepts in the exam. Each question has been selected to match the expected difficulty level and IAT 2026 exam pattern, making it an effective resource for last-minute revision and self-assessment.
IAT 2026 Physics 50 Most Important Questions
Candidates appearing for the IAT 2026 exam can check out the 50 most important Physics questions here. These questions will help candidates strengthen and excel in the topics they have previously studied.
In a Hydrogen atom, the ratio of the radius of the nth orbit to the ground state radius (r1) is found to be 16 : 1. If the electron then makes a transition from this state n to the n = 2 state, what is the energy of the emitted photon?
(A) 1.89 eV Question 2
(B) 2.55 eV
(C) 10.2 eV
(D) 0.66 eV
A particle of mass m moves in a circular orbit in a central potential field U(r) = 1/2kr2. If Bohr’s quantization conditions are applied, radii of possible orbitals and energy levels vary with quantum number n as
(A) rn ∝ n,En ∝ n
(B) (B) rn ∝ √n,En ∝ n
(C) rn ∝ √n,En ∝ 1/n
(D) rn ∝ n2,En ∝ 1/n2
A fusion reactor produces energy by fusing two nuclei of element X (A = 4) into a single nucleus Y (A = 8). The binding energy per nucleon of X is 7.0 MeV and for Y is 8.2 MeV. How many such fusion reactions are required to power a 100 W light bulb for exactly one hour?
(A) 3.75 ×1016
(B) 2.34 ×1017
(C) 3.90 ×1013
(D) 2.34 ×1020
When monochromatic light of wavelength λ illuminates a metal surface, then the stopping potential for photoelectric current is 3V0. If the wavelength changes to 2λ, then the stopping potential becomes V0. Threshold wavelength for photoelectric emission is:
(A) 4λ
(B) 8λ
(C) 4/3λ
(D) 6λ
An ideal gas at 27◦C is compressed adiabatically to 8/27. If γ = 5/3 , then the rise in temperature is:
(A) 450◦C
(B) 375◦C
(C) 225◦C
(D) 405◦C
A gas is expanded from volume V0 to 2V0 under three different processes. Process 1 is isobaric process, process 2 is isothermal and process 3 is adiabatic. Let ∆U1,∆U2 and ∆U3 be the change in internal energy of the gas in these processes. Then:
(A) ∆U1 > ∆U2 >∆U3
(B) ∆U1 < ∆U2 <∆U3
(C) ∆U2 < ∆U1 <∆U3
(D) ∆U2 <∆U3 <∆U1
Arigid, insulated vessel contains a mixture of n moles of Helium (f = 3) and 2n moles of Hydrogen (H2,f = 5). If the temperature of the system is raised by ∆T, the total change in the internal energy of the mixture (∆Utotal) is:
(A) 3nR∆T
(B) 13 2 nR∆T
(C) 4nR∆T
(D) 13 3 nR∆T
Helium gas in a container of fixed volume V is heated such that its absolute temperature T is quadrupled (T → 4T). If λ is the mean free path and λdb is the average de Broglie wavelength, the new values λ′ and λ′ db will be:
(A) λ′ = λ;λ′ db = 1 4λdb
(B) λ′ = 4λ;λ′ db = 1 2λdb
(C) λ′ = λ;λ′ db = 1 2λdb
(D) λ′ = 2λ;λ′ db = λdb
A Carnot engine E (operating between 600 K and 300 K) drives a Carnot refrigerator R (operating between 300 K and 250 K). If E absorbs 1000 J from its source, the total heat rejected into the common 300 K reservoir is:
(A) 2500 J
(B) 3000 J
(C) 3500 J
(D) 4000 J
In the circuit shown below, the bottom wire is taken as the reference ground (0 V). What is the electric potential at Node B?
(A) 0 V
(B)-10 V
(C)-12 V
(D) 15 V
In the circuit shown below, determine the potential difference VA −VB once the system has reached a steady state.
(A) 4 V
(B) 6 V
(C) 5 V
(D) zero
In the circuit diagram shown below, the key K is switched on at t = 0. The ratio of the current i through the cell at t = 0 to that at t = ∞ will be:
(A) 3 : 1
(B) 1 : 3
(C) 1 : 2
(D) 2 :1
The circuit shown below contains two oppositely connected ideal diodes in parallel. What is the current flowing in the circuit?
A) 1.33 A
(B) 1.71 A
(C) 2.00 A
(D) 2.31 A
A solid sphere of radius R has a charge Q distributed in its volume with a charge density ρ = kra, where k and a are constants and r is the distance from its centre. If the electric field at r = R/2 is 1/8 times that at r = R, find the value of a.
(A) 2
(B) 3
(C) 1
(D) 0
A point charge q = +2µC is at the center of a conducting spherical shell with inner radius R1 = 10cm and outer radius R2 = 20cm. The shell has a net charge Q = +4µC. What is the electric potential V at a distance r =15cm from the center?
(A) 120 kV
(B) 270 kV
(C) 360 kV
(D) 540 kV
Download SciAstra App to Practice 50 Most Important Physics Questions with Answers
Strengthen your IAT 2026 preparation with a specially curated set of 50 high-priority Physics questions designed by top mentors and exam experts. Covering important topics like Laws of Motion, Electrostatics, Ray Optics, SHM, Heat & Thermodynamics, Atomic Physics, and EMI, these questions focus on improving conceptual clarity, problem-solving speed, and exam confidence. Practice with detailed solutions and revise the most scoring areas for the IISER Aptitude Test in one place.
Unlock the complete question set now on the SciAstra App and supercharge your IAT 2026 preparation- Click Here
Candidates can check out the detailed explainations to the answer from the SciAstra YouTube Video from here:
Conclusion
The IAT 2026 Physics 50 Most Important Questions serve as an excellent resource for candidates aiming to strengthen their preparation in the final phase before the examination. These carefully selected questions cover the most important concepts, formulas, and problem-solving approaches frequently asked in the IISER Aptitude Test.
By practicing these questions regularly, candidates can improve their conceptual clarity, enhance speed and accuracy, and gain confidence for the actual exam. Physics is often considered one of the most challenging sections of the IAT exam, making strategic revision extremely important. Consistent practice and smart revision can significantly boost overall performance in the examination. With proper preparation and dedication, aspirants can maximise their chances of securing admission to prestigious IISER institutes through IAT 2026.
