CUET · PHYSICS · PYQ PAPER 2025

An electron revolves around a very long line charge having density \( 2 \times 10^{-6} \, Cm^{-1} \). The kinetic energy of the electron is

A \(5 \times 10^{-17} \, J \)
B \(2.88 \times 10^{-16} \, J \)
C \(2.88 \times 10^{-15} \, J \)
D \(5 \times 10^{-15} \, J \)

Verified Solution

Answer & Solution

Correct Answer

(C) \(2.88 \times 10^{-15} \, J \)

Step-by-step Solution

Detailed explanation

\( KE = \frac{q\lambda}{4\pi\epsilon_0} \) \( KE = (1.602 \times 10^{-19} \, C)(2 \times 10^{-6} \, Cm^{-1})(9 \times 10^9 \, Nm^2C^{-2}) \) \( KE = 2.88 \times 10^{-15} \, J \)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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(C) Organisms produce large number of small sized offspring	(III) Salmon fish and bamboo
(D) Some organisms show behavioral responses with variation in their environment	(IV) Birds and mammals

Choose the correct answer from the options given below:

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Luxury Car	Price of the Car (in Rs.)	Down payment (in Rs.)
P	25,00,000	5,00,000
Q	35,00,000	12,00,000
R	45,00,000	15,00,000
S	42,00,000	15,00,000

List-I (Luxury Car)	List-II (EMI (in Rs.))
(A) P	(i) 34,182
(B) Q	(ii) 37,980
(C) R	(iii) 29,118
(D) S	(iv) 25,320