Magnetic Effects of Current - NEET Physics Questions
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Magnetic Effects of Current

Question 31: moderate

Two wires AO and OC carry equal currents i as shown in figure. One end of both the wire extends to infinity. Angle AOC is Ξ±. The magnitude of magnetic field at a point P on the bisector of these two wires at a distance r from point O is :

1. \[\frac{\mu_{0}i}{2\pi r}cot\left( \frac{\alpha}{4} \right)\]
2. \[\frac{\mu_{0}}{4\pi }\frac{i}{r}cot\left( \frac{\alpha}{2} \right)\]
3. \[\frac{\mu_{0}}{4\pi }\frac{i}{r}\frac{\left(1-cos \frac{\alpha}{2} \right)}{sin\left( \frac{\alpha}{2} \right)}\]
4. \[\frac{\mu_{0}}{4\pi }\frac{i}{r}\left( \frac{\alpha}{2} \right)\]
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Question 32: moderate

Two very thin metallic wires placed along X and Y-axis carry equal currents as shown in figure. AB and CD are lines at 45ΒΊ with the axes with origin of axes of O. The magnetic fields will be zero on the line :

1. AB
2. CD
3. Segment OB only of line AB
4. Segment OC only of line CD
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Question 33: moderate

A wire is bent in the form of a circular arc with a straight portion AB. Magnetic induction at O
when current I is flowing in the wire, is :

1. \[\frac{\mu_{0}}{2r}\left( \pi-\theta+tan\theta \right)\]
2. \[\frac{\mu_{0}I}{2\pi r}\left( \pi+\theta-tan\theta \right)\]
3. \[\frac{\mu_{0}I}{2\pi r}\left( \pi-\theta+tan\theta \right)\]
4. \[\frac{\mu_{0}I}{2\pi r}\left( -tan\theta+\pi-\theta \right)\]
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Question 34: moderate

Six wires of current I1 = 1A, I2 = 2A, I3 = 3A, I4 = 1A, I5 = 4A, I6 = 5A cut the page perpendicular at points 1,2,3,4,5 and 6. The value of time integral of \(\overrightarrow{B}\) around the dotted closed path \(\left( i.e, \oint_{}^{}\overrightarrow{B} \overrightarrow{dl} \right)\)Β  is :

1. zero
2. \[\mu_{0} wb m^{-1}\]
3. \[2\mu_{0} wb m^{-1}\]
4. \[4\mu_{0} wb m^{-1}\]
View Answer

current enclosed is (1+2+3-1-4)= 1A

using ampere circuital law we get the answer.

Question 35: moderate

A wire carrying current I has the configuration as shown in Fig. Two semi-infinite straight
sections both tangent to the same circle are connected by a circular arc of central angle ΞΈ,
along the circumference of the circle, with all sections lying in the same plane. If the magnetic
field at the centre of the circle is zero, then ΞΈ is:

1. Ο€/2 rad
2. 2/Ο€ rad
3. 2 rad
4. 1 rad
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Question 36: moderate

In the given diagram, ratio of magnetic field at point A and B will be :

1. 8
2. 1/2√2
3. 3
4. 4
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Question 37: moderate

In the given diagram a rod is rotating with angular velocity Ο‰. Mass of this rod is m, charge q, and length is l then find out magnetic moment of this rod :

1. \[\frac{q\omega l^{2}}{6}\]
2. \[\frac{q\omega l^{2}}{2}\]
3. \[\frac{q\omega l^{2}}{3}\]
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Question 38: moderate

In the above figure magnetic field at point C will be:

1. \[\frac{\mu_{0}i}{2\pi r}\left[ \left( 1+\pi \right)\hat{k}+\hat{i} \right]\]
2. \[\frac{\mu_{0}i}{4\pi r}\left[ \left( 1+\pi \right)\hat{k}-\hat{i} \right]\]
3. \[\frac{\mu_{0}i}{2\pi r}\left[ \left( 1+\pi \right)\hat{k}-\hat{i} \right]\]
4. \[\frac{\mu_{0}i}{4\pi r}\left[ \left( 1-\pi \right)\hat{k}+\hat{i} \right]\]
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Question 39: moderate

A proton is moving along y-axis with velocity 200 m/s & magnetic field of magnitude 1 ΞΌT is acting at 30Β° angle to the y-axis. Then radius of circle in its helical path will be :

1. 2 m
2. 1 cm
3. 1 m
4. 0.1 m
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Question 40: moderate

An eΘ is moving in a zero gravity region towards upward direction & magnetic field in this region is along east direction. Then what will be the direction of electric field in this region so that eΘ can remain undeflected :

1. North
2. South
3. East
4. West
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