Quiz-19-magnetic-effect-of-current-&-magnetism

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MAGNETISM AND MATTER Quiz-19

Dear Readers,

As per analysis for previous years, it has been observed that students preparing for NEET find Physics out of all the sections to be complex to handle and the majority of them are not able to comprehend the reason behind it. This problem arises especially because these aspirants appearing for the examination are more inclined to have a keen interest in Biology due to their medical background. Furthermore, sections such as Physics are dominantly based on theories, laws, numerical in comparison to a section of Biology which is more of fact-based, life sciences, and includes substantial explanations. By using the table given below, you easily and directly access to the topics and respective links of MCQs. Moreover, to make learning smooth and efficient, all the questions come with their supportive solutions to make utilization of time even more productive. Students will be covered for all their studies as the topics are available from basics to even the most advanced. .

Q1. A very long magnet is placed vertically with one pole on the table. A neutral point was found at 20 cm from the pole. What is the pole strength if the vertical component of earth’s field is 0.4×10^-4 Wbm^-2?

•  16 A-m
•  8 A-m
•  4 A-m
•  None of these

Solution
At neutral point, μ₀/4π×m/d² =V 10^-7×m/(20/100)₂ =0.4×10^-4 m=(0.4×10^-4)/(25×10^-7)=16 A-m

Q2. The only property possessed by ferromagnetic substance is

•  Hysteresis
•  Susceptibility
•  Directional property
•  Attracting magnetic substances

Solution
It is a fact.

Q3. The mathematical equation for magnetic field lines of force is

•  ∇ ⃗∙B ⃗=0
•  ∇ ⃗∙B ⃗≠0 1
•  ∇ ⃗∙B ⃗>0
•  ∇ ⃗∙B ⃗<0

Solution
It is a fact.

Q4. The hysteresis cycle for the material of permanent magnet is

•  Short and wide
•  Tall and narrow
•  Tall and wide
•  Short and narrow

Solution
Permanent magnet should have large coercivity and large retentivity. Therefore, the hysteresis cycle of the material should be tall and wide.

Q5.An electron moving around the nucleus with an angular momentum l has a magnetic moment

•  e/m l
•  e/2m l
•  2e/m l
•  e/2πm l

Solution
 An electron moving around the nucleus has a magnetic moment μ given by μ=e/2m l Where l is the magnitude of the angular momentum of the circulating electron around the nucleus. The smallest value of μ is called the bohr magneton μ_B and its value is μ_B=9.27×10^-24JT^-1

Q6. The magnetic susceptibility of a material of a rod is 499. The absolute permeability of vacuum is 4π×10^-7 HM^-1. The absolute permeability of the material of a road is

•  π×10^-4HM^-1
•  2π×10^-4HM^-1
• 3π×10^-4HM^-1
•  4π×10^-4HM^-1

Solution
Absolute permeability of material of rod μ=μ_r μ₀=(1+X_m) μ₀ ∴ μ=(1+499)×4π×10^-7=2π×10^-4 Hm^-1

Q7.The work done in turning a magnet of magnetic moment ‘M’ by an angle of 90° from the meridian is ‘n’ times the corresponding work done to turn it through an angle at 60°, when ‘n’ is given by

•  1/2
•  2
•  1/4
•  1

Solution
W₁=MB(cos⁡0°-cos⁡90°)=MB(1-0)=MB W₂=MB(cos⁡0°-cos⁡60°)=MB(1-1/2)=MB/2 ∴W₁=2W₂⇒n=2

Q8.A magnet of magnetic moment 20 CGS units is freely suspended in a uniform magnetic field of intensity 0.3 CGS units. The amount of work done in deflecting it by an angle of 30° in CGS units is

•  6
•  3√3
•  3(2-√3)
•  3

Solution
Work done, W=MB.(1-cos⁡θ ) =20×0.3(1- cos⁡30°) =6(1-√3/2)=3(2-√3)

Q9.The magnetic force required to demagnetize the material is

•  Retaintivity
•  Coercivity
•  Energy loss
•  Hysteresis

Solution
The coercivity of a substance is a measure of the reverse magnetizing field required to destroy the residual magnetism of the substance.

Q10. The angle between magnetic meridian and geographical meridian is known as

•  Magnetic dip
•  Magnetic latitude
•  Magnetic Declination
• Magnetic longitude

Solution
It is a fact.