CUET · PHYSICS · PYQ PAPER 2025

Two point charges of \( 1 \times 10^{-6} \, C \) and \( 4 \times 10^{-6} \, C \) are placed at a certain distance away from each other. The resultant electric field intensity is zero at a distance of 15 cm from the charge \( 1 \times 10^{-6} \, C \). The distance between the two point charges will be :

A 15 cm
B 30 cm
C 45 cm
D 5 cm

Verified Solution

Answer & Solution

Correct Answer

(C) 45 cm

Step-by-step Solution

Detailed explanation

\( \frac{k q_1}{r_1^2} = \frac{k q_2}{(d - r_1)^2} \) \( \frac{1 \times 10^{-6}}{(15 \, cm)^2} = \frac{4 \times 10^{-6}}{(d - 15 \, cm)^2} \) \( \frac{1}{15} = \frac{2}{d - 15} \) \( d - 15 = 30 \) \( d = 45 \, cm \)

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.

Same subject

Explore more questions on app

From CUET

Explore more questions on app

List-I (Materials)	List-II (Band Gap (eV))
(A) Germanium	(I) 1.42 eV
(B) Gallium Arsenide	(II) > 3 eV
(C) Insulator	(III) 1.1 eV
(D) Silicon	(IV) 0.7 eV