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JEE PHYSICS MCQ: MAGNETIC EFFECT OF CURRENT
1
Medium
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Understanding
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Armature current is maximum in a DC motor when the motor has
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Correct option: B
just started
Option B (just started) is correct because at the moment the DC motor starts, the back EMF is zero, resulting in maximum armature current.
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A needle made of bismuth is suspended freely in a magnetic field. The angle which the needle makes with the magnetic field is:
Assertion: If a charged particles is moving in perpendicular uniform magnetic field, its kinetic energy does not change
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 :