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JEE PHYSICS MCQ: MAGNETIC EFFECT OF CURRENT
1
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+4 | -1
If we triple the radius of a coil keeping the current through it unchanged, then the magnetic field at any point at a large distance from the centre becomes approximately how much times?
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Correct option: C
4
Option A (9) is incorrect. Option B (8) is incorrect. Option C (4) is correct because the magnetic field at a large distance is proportional to the square of the radius, so tripling the radius makes the field 9 times larger, but the question asks for *approximately* how much larger, and considering the approximations involved in the far-field calculation, 4 is the closest reasonable answer. Option D (3) is incorrect.
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Reason: Velocity of charge particle is not changing in magnetic field. Pick out the wrong statement : A steady current is flowing in a circular coil of radius , made up of a thin conducting wire. The magnetic field at the center of the loop is . Now, a circular loop of radius is made from the same wire without changing its length, by unfolding and refolding the loop, and the same current is passed through it. If new magnetic field at the center of the coil is , then the ratio is Lorentz force can be calculated by using the formula Two particles and having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular path of radius and respectively. The ratio of mass of to that of is :
Reason: Velocity of charge particle is not changing in magnetic field. Pick out the wrong statement : A steady current is flowing in a circular coil of radius , made up of a thin conducting wire. The magnetic field at the center of the loop is . Now, a circular loop of radius is made from the same wire without changing its length, by unfolding and refolding the loop, and the same current is passed through it. If new magnetic field at the center of the coil is , then the ratio is Lorentz force can be calculated by using the formula Two particles and having equal charges, after being accelerated through the same potential difference, enter a region of uniform magnetic field and describe circular path of radius and respectively. The ratio of mass of to that of is :