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Question 14

A coil is placed in magnetic field such that plane of coil is perpendicular to the direction of magnetic field. The magnetic flux through a coil can be changed:
A. By changing the magnitude of the magnetic field within the coil.
B. By changing the area of coil within the magnetic field.
C. By changing the angle between the direction of magnetic field and the plane of the coil.
D. By reversing the magnetic field direction abruptly without changing its magnitude.
Choose the most appropriate answer from the options given below:

$$\Phi = B A \cos(\theta)$$:

Statement A: Changing the magnitude of the magnetic field ($$B$$) directly scales the flux. (Correct)

Statement B: Changing the area of the coil ($$A$$) directly scales the flux. (Correct)

Statement C: Changing the angle alters the $$\cos(\theta)$$ term. If the plane is initially perpendicular ($$\theta = 0^\circ$$), rotating it will decrease the flux. This is the exact principle behind how AC generators produce electricity. (Correct)

Statement D: Reversing the magnetic field changes its direction by $$180^\circ$$. The flux changes from $$+BA$$ to $$-BA$$. Since flux is a scalar, this represents a net change of $$\Delta \Phi = -2BA$$. (Correct)

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