CUET · PHYSICS · PYQ PAPER 2023

A coil and a bulb are connected in series with a dc source. When a soft iron piece is inserted in the coil. Then,

A Intensity of the bulb remains the same
B Intensity of the bulb decreases
C Intensity of the bulb increases
D The bulb ceases to glow

Verified Solution

Answer & Solution

Correct Answer

(A) Intensity of the bulb remains the same

Step-by-step Solution

Detailed explanation

The DC resistance of the coil does not change by inserting a soft iron core. Therefore, the total resistance of the circuit remains constant. Current \( I = V/R_{total} \) remains constant. Intensity of the bulb remains the same.

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

Match List - I with List - II.

List - I	List - II
(A) \( \oint \vec{B} \cdot d\vec{A} = 0 \)	(I) Gauss's Law of electricity
(B) \( \oint \vec{E} \cdot d\vec{A} = \frac{Q}{\epsilon_0} \)	(II) Gauss's Law of magnetism
(C) \( \oint \vec{B} \cdot dl = \mu_0 i_c + \mu_0 \epsilon_0 \frac{d\phi_E}{dt} \)	(III) Faraday's Law
(D) \( \oint \vec{E} \cdot dl = -\frac{d\phi_B}{dt} \)	(IV) Ampere-Maxwell Law

Choose the correct answer from the options given below :

CUET 2023 Medium

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From CUET

Match List-I with List-I

List-I	List-II
A. Electric field outside a uniformly charged thin spherical shell	(I) zero
B. Electric field inside a uniformly charged thin spherical shell	(II) \(\frac{\lambda}{2 \pi \epsilon_0 r} \vec{n}\)
C. Electric field due to an infinitely long straight uniformly charged wire	(III) \(\frac{\sigma}{2 \epsilon_0} \vec{n}\)
D. Electric field due to a uniformly charged infinite plane sheet	(IV) \(\frac{k q}{r^2} \vec{r}\)

Choose the correct answer from the options given below:

CUET 2023 Medium

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