Magnetic Effects of Current & Magnetism · JEE Main previous year questions

2019 22 questions

1. Q342019 · 12 Apr 2019 · Shift 1

   A thin ring of 10 cm radius carries a uniformly distributed charge. The ring rotates at a constant angular speed of $40\pi {\text{ rad s}}^{-1}$ about its axis, perpendicular to its plane. If the magnetic field at its centre is $3.8\times 10^{-9}\text{ T}$, then the charge carried by the ring is close to (${\mu }_0=4\pi \times 10^{-7}{\text{ N/A}}^2$).

   1. A.$7\times 10^{-6}\text{ C}$
   2. B.$4\times 10^{-5}\text{ C}$
   3. C.$2\times 10^{-6}\text{ C}$
   4. D.$3\times 10^{-5}\text{ C}$
   Show answer

   Answer: D

2. Q582019 · 12 Apr 2019 · Shift 1

   A magnetic compass needle oscillates 30 times per minute at a place where the dip is $45^{\circ }$, and 40 times per minute where the dip is $30^{\circ }$. If $B_1$ and $B_2$ are respectively the total magnetic field due to the earth at the two places, then the ratio $\frac{B_1}{B_2}$ is best given by :

   1. A.1.8
   2. B.2.2
   3. C.0.7
   4. D.3.6
   Show answer

   Answer: C

3. Q462019 · 12 Apr 2019 · Shift 2
   
   1. A.2.25 cm
   2. B.12.87 cm
   3. C.1.22 cm
   4. D.11.65 cm
   Show answer

   Answer: B

4. Q512019 · 12 Apr 2019 · Shift 2
   
   1. A.$1.5\times 10^{-5}\text{ T}$
   2. B.$3.0\times 10^{-5}\text{ T}$
   3. C.$2.0\times 10^{-5}\text{ T}$
   4. D.$2.5\times 10^{-5}\text{ T}$
   Show answer

   Answer: A

5. Q402019 · 10 Apr 2019 · Shift 1

   A proton, an electron, and a Helium nucleus, have the same energy. They are in circular orbits in a plane due to magnetic field perpendicualr to the plane. Let ${\mathrm{r}}_{\mathrm{p}}$, ${\mathrm{r}}_{\mathrm{e}}$ and ${\mathrm{r}}_{\mathrm{He}}$ be their respective radii, then

   1. A.${\mathrm{r}}_{\mathrm{e}}<{\mathrm{r}}_{\mathrm{p}}<{\mathrm{r}}_{\mathrm{He}}$
   2. B.${\mathrm{r}}_{\mathrm{e}}<{\mathrm{r}}_{\mathrm{p}}={\mathrm{r}}_{\mathrm{He}}$
   3. C.${\mathrm{r}}_{\mathrm{e}}>{\mathrm{r}}_{\mathrm{p}}>{\mathrm{r}}_{\mathrm{He}}$
   4. D.${\mathrm{r}}_{\mathrm{e}}>{\mathrm{r}}_{\mathrm{p}}={\mathrm{r}}_{\mathrm{He}}$
   Show answer

   Answer: B

6. Q492019 · 10 Apr 2019 · Shift 2

   The magnitude of the magnetic field at the centre of an equilateral triangular loop of side 1 m which is carrying a current of 10 A is : [Take ${\mu }_0=4\pi \times 10^{-7}\mathrm{N}{\mathrm{A}}^{-2}$]

   1. A.$3\mu \mathrm{T}$
   2. B.$18\mu \mathrm{T}$
   3. C.$9\mu \mathrm{T}$
   4. D.$1\mu \mathrm{T}$
   Show answer

   Answer: B

7. Q352019 · 9 Apr 2019 · Shift 1

   The total number of turns and cross-section area in a solenoid is fixed. However, its length L is varied by adjusting the separation between windings. The inductance of solenoid will be proportional to :

   1. A.$1/L^2$
   2. B.1/L
   3. C.L
   4. D.$L^2$
   Show answer

   Answer: B

8. Q552019 · 9 Apr 2019 · Shift 1

   The magnetic field of a plane electromagnetic wave is given by : $$\vec{B}=B_0\hat{i}[\cos (kz-\omega t)]+B_i\hat{j}\cos (kz+\omega t)$$ $B_0=3\times 10^{-5}\mathrm{T}$ and B1 = $2\times 10^{-6}\mathrm{T}$. The rms value of the force experienced by a stationary charge $Q=10^{-4}\mathrm{C}$ at z = 0 is closest to :

   1. A.0.6 N
   2. B.0.9 N
   3. C.$3\times 10^{-2}\mathrm{N}$
   4. D.0.1 N
   Show answer

   Answer: A

9. Q362019 · 9 Apr 2019 · Shift 2

   A moving coil galvanometer has a coil with 175 turns and area $1\mathrm{c}{\mathrm{m}}^2$. It uses a torsion band of torsion constant $10^{-6}\mathrm{N}\text{-}m/rad$. The coil is placed in a maganetic field B parallel to its plane. The coil deflects by $1^{\circ }$ for a current of 1 mA. The value of B (in Tesla) is approximately :-

   1. A.$10^{-4}$
   2. B.$10^{-2}$
   3. C.$10^{-1}$
   4. D.$10^{-3}$
   Show answer

   Answer: D

10. Q372019 · 9 Apr 2019 · Shift 2
    
    1. A.
    2. B.
    3. C.
    4. D.
    Show answer

    Answer: A

11. Q322019 · 8 Apr 2019 · Shift 2
    
    1. A.$+\frac{{\mu }_{0}I}{\pi d}(\hat{z})$
    2. B.$-\frac{{\mu }_{0}I}{2\pi d}(\hat{x}+\hat{y})$
    3. C.Zero
    4. D.$\frac{{\mu }_{0}I}{2\pi d}(\hat{x}+\hat{y})$
    Show answer

    Answer: C

12. Q312019 · 12 Jan 2019 · Shift 1
    
    1. A.$40\mathrm{A}$, perpendicular into the page
    2. B.$40\mathrm{A}$, perpendicular out of the page
    3. C.$20\mathrm{A}$, perpendicular into the page
    4. D.$20\mathrm{A}$, perpendicular out of the page
    Show answer

    Answer: C

13. Q542019 · 12 Jan 2019 · Shift 1

    A proton and an $\alpha$-particle (with their masses in the ratio of $1:4$ and charges in the ratio of $1:2$) are accelerated from rest through a potential difference V. If a uniform magnetic field (B) is set up perpendicular to their velocities, the ratio of the radii $r_p:r_{\alpha }$ of the circular paths described by them will be ;

    1. A.$1:\sqrt{3}$
    2. B.$1:3$
    3. C.$1:\sqrt{2}$
    4. D.$1:2$
    Show answer

    Answer: C

14. Q482019 · 12 Jan 2019 · Shift 2

    The mean intensity of radiation on the surface of the Sun is about $10^{8}W/{\mathrm{m}}^2$ . The rms value of the corresponding magnetic field is closet to :

    1. A.$10^2\mathrm{T}$
    2. B.$10^{-2}\mathrm{T}$
    3. C.$10^{-4}\mathrm{T}$
    4. D.$1\mathrm{T}$
    Show answer

    Answer: C

15. Q502019 · 12 Jan 2019 · Shift 2

    A 10 m long horizontal wire extends from North East to South West. It is falling with a speed of $5.0\mathrm{m}{\mathrm{s}}^{-1}$, at right angles to the horizontal component of the earth's magnetic field of $0.3\times 10^{-4}Wb/{\mathrm{m}}^2$. The value of the induced emf in wire is :

    1. A.$0.3\times 10^{-3}\mathrm{V}$
    2. B.$2.5\times 10^{-3}\mathrm{V}$
    3. C.$1.5\times 10^{-3}\mathrm{V}$
    4. D.$1.1\times 10^{-3}\mathrm{V}$
    Show answer

    Answer: D

16. Q572019 · 12 Jan 2019 · Shift 2

    A paramagnetic material has $10^{28}atoms/{\mathrm{m}}^3$. Its magnetic susceptibility at temperature 350 K is $2.8\times 10^{-4}$. Its susceptibility at 300 K is :

    1. A.$3.726\times 10^{-4}$
    2. B.$2.672\times 10^{-4}$
    3. C.$3.672\times 10^{-4}$
    4. D.$3.267\times 10^{-4}$
    Show answer

    Answer: D

17. Q312019 · 11 Jan 2019 · Shift 2

    The region between $y=0$ and $y=d$ contains a magnetic field $\vec{B}=B\hat{z}$. A particle of mass m and charge q enters the region with a velocity $\vec{v}=v\hat{i}$. If $d=\frac{mv}{2qB}$, the acceleration of the charged particle at the point of its emergence at the other side is :

    1. A.$\frac{qvB}{m}\left(-\frac{\sqrt{3}}{2}\hat{i}-\frac{1}{2}\hat{j}\right)$
    2. B.$\frac{qvB}{m}\left(\frac{1}{2}\hat{i}-\frac{\sqrt{3}}{2}\hat{j}\right)$
    3. C.$\frac{qvB}{m}\left(\frac{-\hat{j}+\hat{i}}{\sqrt{2}}\right)$
    4. D.$\frac{qvB}{m}\left(\frac{\hat{j}+\hat{i}}{\sqrt{2}}\right)$
    Show answer

    Answer: A

18. Q472019 · 11 Jan 2019 · Shift 2

    A particle of mass m and charge q is in an electric and magnetic field given by $$\vec{E}=2\hat{i}+3\hat{j};\vec{B}=4\hat{j}+6\hat{k}.$$ The charged particle is shifted from the origin to the point $\mathrm{P}(x=1;y=1)$ along a straight path. The magnitude of the total work done is :

    1. A.(2.5) q
    2. B.(0.35) q
    3. C.(0.15) q
    4. D.5 q
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    Answer: D

19. Q322019 · 9 Jan 2019 · Shift 1
    
    1. A.$1.0\times 10^{-7}\text{ T}$
    2. B.$1.5\times 10^{-7}\text{ T}$
    3. C.$1.5\times 10^{-5}\text{ T}$
    4. D.$1.0\times 10^{-5}\text{ T}$
    Show answer

    Answer: D

20. Q512019 · 9 Jan 2019 · Shift 1
    
    1. A.$F=0$
    2. B.$F\propto \left(\frac{a}{d}\right)$
    3. C.$F\propto \left(\frac{a^2}{d^3}\right)$
    4. D.$F\propto {\left(\frac{a}{d}\right)}^2$
    Show answer

    Answer: D

21. Q522019 · 9 Jan 2019 · Shift 1

    A plane electromagnetic wave of frequency $50\text{ MHz}$ travels in free space along the positive x-direction. At a particular point in space and time, $\vec{E}=6.3\hat{j}\text{ V/m}$. The corresponding magnetic field $\vec{B}$, at that point will be :

    1. A.$18.9\times 10^{-8}\hat{k}\text{ T}$
    2. B.$2.1\times 10^{-8}\hat{k}\text{ T}$
    3. C.$6.3\times 10^{-8}\hat{k}\text{ T}$
    4. D.$18.9\times 10^8\hat{k}\text{ T}$
    Show answer

    Answer: B

22. Q582019 · 9 Jan 2019 · Shift 1

    A bar magnet is demagnetized by inserting it inside a solenoid of length 0.2 m, 100 turns, and carrying a current of 5.2 A. The coercivity of the bar magnet is :

    1. A.285 A/m
    2. B.2600 A/m
    3. C.520 A/m
    4. D.1200 A/m
    Show answer

    Answer: B