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Q. No.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: Magnetic Field due to various cases |
84%
Level 1: 80%+
Hints
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: Magnetic Field due to various cases |
65%
Level 2: 60%+
NEET - 2022
Hints
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: Ampere Circuital Law |
66%
Level 2: 60%+
NEET - 2022
Hints
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: Magnetic Moment |
64%
Level 2: 60%+
NEET - 2022
Hints
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: Lorentz Force |
67%
Level 2: 60%+
NEET - 2022
Hints
Given below are two statements:
| Statement I: | A charged particle moving in a magnetic field experiences a force which is zero only when it moves in the direction of the field or against it. |
| Statement II: | Whenever a charged particle moves in a uniform magnetic field, its trajectory may be a circle, a straight line or a helix. |
| 1. | Statement I is incorrect and 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 and Statement II is incorrect. |
Subtopic: Lorentz Force |
73%
Level 2: 60%+
Hints
The value of unknown resistance \(R\) for which \(20\)% of the main current passes through a galvanometer of resistance \(80\) \(\Omega \) is:
| 1. | \(10\) \(\Omega \) | 2. | \(20\) \(\Omega \) |
| 3. | \(30\) \(\Omega \) | 4. | \(40\) \(\Omega \) |
Subtopic: Conversion to Ammeter & Voltmeter |
86%
Level 1: 80%+
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Hints
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A magnetized wire of magnetic moment \(M\) and length \(L\) is bent in the form of the semi-circle of radius \(r\). The new magnetic moment is:
1. \(M\)
2. \(M / 2 \pi\)
3. \(M / \pi\)
4. \(2M / \pi\)
1. \(M\)
2. \(M / 2 \pi\)
3. \(M / \pi\)
4. \(2M / \pi\)
Subtopic: Magnetic Moment |
53%
Level 3: 35%-60%
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A charged particle is moving in a uniform magnetic field \((2 \hat{i}+3 \hat{j}) ~\text{T} .\) If it has an acceleration of \((\alpha \hat{i}-4 \hat{j})~ \text{m /s}^{2},\) then the value of \(\alpha \) will be:
1. \(3\)
2. \(6\)
3. \(12\)
4. \(2\)
1. \(3\)
2. \(6\)
3. \(12\)
4. \(2\)
Subtopic: Lorentz Force |
87%
Level 1: 80%+
JEE
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Given below are two statements:
| Assertion (A): | In a uniform magnetic field, speed and energy remain the same for a moving charged particle. |
| Reason (R): | Moving charged particle experiences a magnetic force perpendicular to its direction of motion. |
| 1. | Both (A) and (R) are True and (R) is the correct explanation of (A). |
| 2. | Both (A) and (R) are True but (R) is not the correct explanation of (A). |
| 3. | (A) is True but (R) is False. |
| 4. | (A) is False but (R) is True. |
Subtopic: Lorentz Force |
68%
Level 2: 60%+
JEE
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