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Q. No.The magnetic field at a point (\(P\)) on the axis of a circular current-carrying wire is \(\dfrac18\) of the field at its centre. The radius of the circular curve is \(R.\) The distance between \(P\) and the centre of the circle \((OP)\) is:
Then:
1.
\(OP=R\)
2.
\(OP=\dfrac R2\)
3.
\(OP=\sqrt3R \)
4.
\(OP=8R\)
Subtopic: Â Magnetic Field due to various cases |
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Level 2: 60%+
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A current \(i\) flows through a semi-circular loop of radius \(r,\) attached to two long straight wires along the open diameter of the loop. The magnetic field at the centre of the loop is:
| 1. | \(\dfrac{\mu_0i}{4r}\) |
| 2. | \(\dfrac{\mu_0i}{4r}+\dfrac{\mu_0i}{2\pi r}\) |
| 3. | \(\dfrac{\mu_0i}{4r}+\dfrac{\mu_0i}{4\pi r}\) |
| 4. | \(\left[\left(\dfrac{\mu_0i}{4r}\right)^2+\left(\dfrac{\mu_0i}{4\pi r}\right)^2\right]^{\frac12} \) |
Subtopic: Â Magnetic Field due to various cases |
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Level 1: 80%+
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A charged particle moves in a circular path of radius \(r\) in a uniform magnetic field \(B,\) perpendicular to the plane of motion. The same particle is observed to move in a circular path around an infinite line charge \(\lambda\) (charge/unit length), moving with the same kinetic energy as before. The charge to mass ratio of the particle is proportional to:
| 1. | \(\lambda Br\) | 2. | \(\dfrac{\lambda Br}{r}\) |
| 3. | \(\dfrac{\lambda}{Br}\) | 4. | \(\dfrac{\lambda}{B^2r^2}\) |
Subtopic: Â Lorentz Force |
Level 3: 35%-60%
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A galvanometer \(G\) (having very small resistance), when connected with a resistance of \(10~\text k\Omega\) in series, can function as a voltmeter measuring a maximum voltage of \(20\) V. The current required to give a full scale deflection on the galvanometer is:
1. \(0.1\) mA
2. \(0.2\) mA
3. \(1\) mA
4. \(2\) mA
1. \(0.1\) mA
2. \(0.2\) mA
3. \(1\) mA
4. \(2\) mA
Subtopic: Â Moving Coil Galvanometer |
 78%
Level 2: 60%+
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A long solenoid of radius \(1~\text{mm}\) has \(100\) turns per mm. If \(1~\text{A}\) current flows in the solenoid, the magnetic field strength at the centre of the solenoid is:
| 1. | \(6.28 \times 10^{-4} ~\text{T} \) | 2. | \(6.28 \times 10^{-2}~\text{T}\) |
| 3. | \(12.56 \times 10^{-2}~\text{T}\) | 4. | \(12.56 \times 10^{-4} ~\text{T}\) |
Subtopic: Â Magnetic Field due to various cases |
 65%
Level 2: 60%+
NEET - 2022
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Given below are two statements:
| Statement I: | Biot-Savart's law gives us the expression for the magnetic field strength of an infinitesimal current element \((Idl)\) of a current-carrying conductor only. |
| Statement II: | Biot-Savart's law is analogous to Coulomb's inverse square law of charge \(q,\) with the former being related to the field produced by a scalar source, \((Idl)\) while the latter being produced by a vector source, \(q.\) |
| 1. | Statement I is incorrect but Statement II is correct. |
| 2. | Both Statement I and Statement II are correct. |
| 3. | Both Statement I and Statement II are incorrect. |
| 4. | Statement I is correct but Statement II is incorrect. |
Subtopic: Â Biot-Savart Law |
 56%
Level 3: 35%-60%
NEET - 2022
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From Ampere's circuital law, for a long straight wire of circular cross-section carrying a steady-current, the variation of the magnetic field inside and outside the region of the wire is:
| 1. | A linearly decreasing function of distance upto the boundary of the wire and then a linearly increasing one for the outside region. |
| 2. | Uniform and remains constant for both regions. |
| 3. | A linearly increasing function of distance upto the boundary of the wire and then a linearly decreasing one for the outside region. |
| 4. | A linearly increasing function of distance \(r\) upto the boundary of the wire and then decreasing one with \(1/r\) dependence for the outside region. |
Subtopic: Â Ampere Circuital Law |
 66%
Level 2: 60%+
NEET - 2022
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The ratio of the radii of two circular coils is \(1:2.\) The ratio of currents in the respective coils such that the same magnetic moment is produced at the centre of each coil is:
| 1. | \(4:1\) | 2. | \(2:1\) |
| 3. | \(1:2\) | 4. | \(1:4\) |
Subtopic: Â Magnetic Moment |
 64%
Level 2: 60%+
NEET - 2022
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A strong magnetic field is applied along the direction of the velocity of an electron. The electron would move along:
| 1. | a parabolic path |
| 2. | the original path |
| 3. | a helical path |
| 4. | a circular path |
Subtopic: Â Lorentz Force |
 67%
Level 2: 60%+
NEET - 2022
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Two long parallel wires carrying currents \(I_1\) and \(I_2\) give a magnetic field of \(3\) G at a point exactly mid-way between the two wires. When one of the currents is reversed, the field becomes \(5\) G. The ratio of the large current to the smaller one is:
| 1. | \(2\) | 2. | \(\dfrac43\) |
| 3. | \(\dfrac32\) | 4. | \(4\) |
Subtopic: Â Magnetic Field due to various cases |
 75%
Level 2: 60%+
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