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General — JEE Physics MCQs

Master General for JEE Main with free physics MCQs. Each question includes a detailed solution and instant feedback — practice at easy, medium, and hard difficulty levels to build exam-ready confidence.

6 practice questions with instant feedback and solutions.

Hard•General
In a radioactive sample, 1940 K{ }_{19}^{40} \mathrm{~K} nuclei either decay into stable 2040Ca{ }_{20}^{40} \mathrm{Ca} nuclei with decay constant 4.5×10−104.5 \times 10^{-10} per year or into stable 1840Ar{ }_{18}^{40} \mathrm{Ar} nuclei with decay constant 0.5×10−100.5 \times 10^{-10} per year. Given that in this sample all the stable 2040Ca{ }_{20}^{40} \mathrm{Ca} and 1840Ar{ }_{18}^{40} \mathrm{Ar} nuclei are produced by the 1940 K{ }_{19}^{40} \mathrm{~K} nuclei only. In time t×109t \times 10^{9} years, if the ratio of the sum of stable 2040Ca{ }_{20}^{40} \mathrm{Ca} and 1840Ar{ }_{18}^{40} \mathrm{Ar} nuclei to the radioactive 1940 K{ }_{19}^{40} \mathrm{~K} nuclei is 99 , the value of tt will be, [Given: ln⁡10=2.3]\ln 10=2.3]
Hard•General
A thin spherical insulating shell of radius RR carries a uniformly distributed charge such that the potential at its surface is V0V_{0}. A hole with a small area α4πR2(α≪1)\alpha 4 \pi R^{2}(\alpha \ll 1) is made on the shell without affecting the rest of the shell. Which one of the following statements is correct?
Medium•General
An accident in a nuclear laboratory resulted in deposition of a certain amount of radioactive material of half-life 18 days inside the laboratory. Tests revealed that the radiation was 64 times more than the permissible level required for safe operation of the laboratory. What is the minimum number of days after which the laboratory can be considered safe for use?
Medium•General
List-I shows different radioactive decay processes and List-II provides possible emitted particles. Match each entry in List-I with an appropriate entry from List-II, and choose the correct option. List-I\textbf{List-I} (P) 92238U→91234 Pa{ }_{92}^{238} U \rightarrow{ }_{91}^{234} \mathrm{~Pa} (Q) 82214 Pb→82210 Pb{ }_{82}^{214} \mathrm{~Pb} \rightarrow{ }_{82}^{210} \mathrm{~Pb} (R) 81210Tl→82206 Pb{ }_{81}^{210} \mathrm{Tl} \rightarrow{ }_{82}^{206} \mathrm{~Pb} (S) 91228 Pa→88224Ra{ }_{91}^{228} \mathrm{~Pa} \rightarrow{ }_{88}^{224} \mathrm{Ra} List-II\textbf{List-II} (1) one α\alpha particle and one β+\beta^{+}particle (2) three β−\beta^{-}particles and one α\alpha particle (3) two β−\beta^{-}particles and one α\alpha particle (4) one α\alpha particle and one β−\beta^{-}particle (5) one α\alpha particle and two β+\beta^{+}particles
Medium•General
A heavy nucleus QQ of half-life 20 minutes undergoes alpha-decay with probability of 60%60 \% and beta-decay with probability of 40%40 \%. Initially, the number of QQ nuclei is 1000. The number of alpha-decays of QQ in the first one hour is
Medium•General
Area of the cross-section of a wire is measured using a screw gauge. The pitch of the main scale is 0.5 mm0.5 \mathrm{~mm}. The circular scale has 100 divisions and for one full rotation of the circular scale, the main scale shifts by two divisions. The measured readings are listed below.
Measurement conditionMain scale readingCircular scale reading
Two arms of gauge touching each other without wire0 division4 divisions
Attempt-1: With wire4 divisions20 divisions
Attempt-2: With wire4 divisions16 divisions
What are the diameter and cross-sectional area of the wire measured using the screw gauge?