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Q. No.The \(B\text{-}H\) curve for a ferromagnet is shown in the figure. The ferromagnet is placed inside a long solenoid with \(1000~ \text{turns/cm.}\) The current that should be passed in the solenoid to demagnetise the ferromagnet completely is :
1. \(2~\text{mA}\)
2. \(20~\mu\text{A}\)
3. \(1~\text{mA}\)
4. \(40~\mu\text{A}\)
1. \(2~\text{mA}\)
2. \(20~\mu\text{A}\)
3. \(1~\text{mA}\)
4. \(40~\mu\text{A}\)
Subtopic: Â Magnetic Materials |
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Level 2: 60%+
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Magnetic materials used for making permanent magnets (\(\text{P}\)) and magnets in a transformer (\(\text{T}\)) have different properties of the following, which property best matches for the type of magnet required?
| 1. | \(\text{T}\) : Large retentivity, small coercivity |
| 2. | \(\text{P}\) : Small retentivity, large coercivity |
| 3. | \(\text{T}\) : Large retentivity, large coercivity |
| 4. | \(\text{P}\) : Large retentivity, large coercivity |
Subtopic: Â Magnetic Materials |
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Level 2: 60%+
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A perfectly diamagnetic sphere has a small spherical cavity at its centre, which is filled with a paramagnetic substance. The whole system is placed in a uniform magnetic field \(\vec{B}\). Then the field inside the paramagnetic substance is:
| 1. | Zero |
| 2. | \(\vec{B}\) |
| 3. | much larger than \(|\vec{B}|\) and parallel to \(\vec{B}\) |
| 4. | much larger than \(|\vec{B}|\) and opposite to \(\vec{B}\) |
Subtopic: Â Magnetic Materials |
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Level 2: 60%+
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A soft ferromagnetic material is placed in an external magnetic field. The magnetic domains:
| 1. | increase in size but no change in orientation |
| 2. | have no relation with an external magnetic field |
| 3. | decrease in size and change its orientation |
| 4. | may increase or decrease in size and change its orientation |
Subtopic: Â Magnetic Materials |
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Level 2: 60%+
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In a ferromagnetic material, below the curie temperature, a domain is defined as:
| 1. | a macroscopic region with zero magnetization. |
| 2. | a macroscopic region with consecutive magnetic dipoles oriented in opposite directions. |
| 3. | a macroscopic region with randomly oriented magnetic dipoles. |
| 4. | a macroscopic region with saturation magnetization. |
Subtopic: Â Magnetic Materials |
Level 3: 35%-60%
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The susceptibility of a paramagnetic material is \(99.\) The permeability of the material in Wb/A-m is:
(Permeability of free space, \(\mu_{0}=4\pi \times 10^{-7}\) Wb/A-m )
1. \(4 \pi \times 10^{-7} \)
2. \( 4 \pi \times 10^{-4} \)
3. \( 4 \pi \times 10^{-5} \)
4. \( 4 \pi \times 10^{-6}\)
(Permeability of free space, \(\mu_{0}=4\pi \times 10^{-7}\) Wb/A-m )
1. \(4 \pi \times 10^{-7} \)
2. \( 4 \pi \times 10^{-4} \)
3. \( 4 \pi \times 10^{-5} \)
4. \( 4 \pi \times 10^{-6}\)
Subtopic: Â Magnetic Materials |
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Level 1: 80%+
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Given below two statements:
| Statement I: | For diamagnetic substances, \(-1 \leq \chi <0 ,\) where \(\chi\) is the magnetic susceptibility. |
| Statement II: | Diamagnetic substances, when placed in an external magnetic field, tend to move from the stronger to the weaker part of the field. |
| 1. | Both Statement I and Statement II are correct. |
| 2. | Both Statement I and Statement II are incorrect. |
| 3. | Statement I is correct, and Statement II is incorrect. |
| 4. | Statement I is incorrect, and Statement II is correct. |
Subtopic: Â Magnetic Materials |
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Level 1: 80%+
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Match List-I with List-II
Choose the correct answer from the options given below :
| List - I | List - II | ||
| A | \(Y= \)magnetic susceptibility \(X=\) magnetizing field |
I |  |
| B | \(Y= \) magnetic field \(X=\) distance from centre of a current carrying wire for \(x<a\) (where \(a=\) radius of wire) |
II |  |
| C | \(Y= \) magnetic field \(X=\) distance from centre of a current carrying wire for \(x>a\) (where \(a=\) radius of wire) |
III |  |
| D | \(Y= \) magnetic field inside solenoid \(X=\) distance from centre |
IV |  |
Choose the correct answer from the options given below :
1. (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
2. (A)-(III), (B)-(IV), (C)-(I), (D)-(II)
3. (A)-(I), (B)-(III), (C)-(II), (D)-(IV)
4. (A)-(IV), (B)-(I), (C)-(III), (D)-(II)
Subtopic: Â Magnetic Materials |
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Level 3: 35%-60%
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Paramagnetic substances:
Choose the most appropriate answer from the options given below:
1. (A), (C) only
2. (B), (D) only
3. (A), (B), (C), (D)
4. (A), (B), (C) only
| (A) | Align themselves along the directions of the external magnetic field. |
| (B) | Attract strongly towards an external magnetic field. |
| (C) | Has susceptibility little more than zero. |
| (D) | Move from a region of strong magnetic field to a weak magnetic field. |
Choose the most appropriate answer from the options given below:
1. (A), (C) only
2. (B), (D) only
3. (A), (B), (C), (D)
4. (A), (B), (C) only
Subtopic: Â Magnetic Materials |
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Level 2: 60%+
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