CBSE Class 12 Physics Electromagnetic Induction Q #2086
COMPETENCY BASED
APPLY
1 Marks 2026 AISSCE(Board Exam) MCQ SINGLE
A square loop of side 50 cm is placed in a uniform magnetic field of $3\cdot 0$ T acting perpendicular to the plane of the loop. If the loop is rotated through an angle of $90^{\circ}$ in $0\cdot 3$ s, the value of emf induced in the loop would be :
(A) $2\cdot 5$ V
(B) $0\cdot 50$ V
(C) $0\cdot 75$ V
(D) $1\cdot 0$ V
Correct Answer: A

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Detailed Solution

Step 1: Identify Given Parameters

Side of the square loop $a = 50\text{ cm} = 0.5\text{ m}$. Area $A = a^2 = (0.5)^2 = 0.25\text{ m}^2$. Magnetic field $B = 3.0\text{ T}$. Time interval $\Delta t = 0.3\text{ s}$.

Step 2: Calculate Initial and Final Magnetic Flux

Initial flux $\phi_i = B \cdot A \cdot \cos(0^{\circ}) = 3.0 \times 0.25 \times 1 = 0.75\text{ Wb}$. Since the loop is rotated by $90^{\circ}$, the final flux $\phi_f = B \cdot A \cdot \cos(90^{\circ}) = 0\text{ Wb}$.

Step 3: Apply Faraday's Law of Induction

The induced emf is given by the magnitude of the rate of change of magnetic flux: $$|\varepsilon| = \left| \frac{\Delta \phi}{\Delta t} \right| = \left| \frac{\phi_f - \phi_i}{\Delta t} \right|$$

Step 4: Final Calculation

Substituting the values: $$|\varepsilon| = \left| \frac{0 - 0.75}{0.3} \right| = \frac{0.75}{0.3} = 2.5\text{ V}$$

Final Answer: 2.5 V

AI Suggestion: Option A

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student must translate the physical scenario into a mathematical model using Faraday's Law of Induction.
Knowledge Dimension: PROCEDURAL
Justification: The problem requires a step-by-step algorithmic approach involving area calculation, flux determination, and differentiation (rate of change).
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. It tests the student's ability to apply electromagnetic induction principles to a specific geometric configuration.

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