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

2018 6 questions

1. Q442018 · 16 Apr 2018 · Shift 1

   A coil of cross-sectional area A having n turns is placed in a uniform magnetic field B. When it is rotated with an angular velocity $\omega$, the maxium e.m.f. induced in the coil will be:

   1. A.$3\text{nBA}\omega$
   2. B.$\frac{3}{2}\text{nBA}\omega$
   3. C.$\text{nBA}\omega$
   4. D.$\frac{1}{2}\text{nBA}\omega$
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   Answer: C

2. Q472018 · 16 Apr 2018 · Shift 1

   A plane electromagnetic wave of wavelength $\lambda$ has an intensity I. It is propagatting along the positive Y-direction. The allowed expressions for the electric and magnetic fields are givn by :

   1. A.$\vec{E}=\sqrt{\frac{2I}{{ϵ}_{0}C}}\cos \left[\frac{2\pi }{\lambda }(y-ct)\right]\hat{k};\vec{B}=+\frac{1}{c}E\hat{i}$
   2. B.$\vec{E}=\sqrt{\frac{2I}{{ϵ}_{0}c}}\cos \left[\frac{2\pi }{\lambda }(y+ct)\right]\hat{k};\vec{B}=-\frac{1}{c}E\hat{i}$
   3. C.$\vec{E}=\sqrt{\frac{I}{{ϵ}_{0}c}}\cos \left[\frac{2\pi }{\lambda }(y-ct)\right]\hat{k};\vec{B}=-\frac{1}{c}E\hat{i}$
   4. D.$\vec{E}=\sqrt{\frac{I}{{ϵ}_{0}c}}\cos \left[\frac{2\pi }{\lambda }(y-ct)\right]\hat{i};\vec{B}=\frac{1}{c}E\hat{k}$
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   Answer: A

3. Q402018 · 15 Apr 2018 · Shift 1

   A monochromatic beam of light has a frequency $\nu =\frac{3}{2\pi }\times 10^{12}Hz$ and is propagating along the direction $\frac{\hat{i}+\hat{j}}{\sqrt{2}}$. It is polarized along the $\hat{k}$ direction. The acceptable form for the magnetic field is :

   1. A.$\frac{E_o}{C}\frac{(\hat{i}-\hat{j})}{\sqrt{2}}\cos \left[10^4\frac{(\hat{i}+\hat{j})}{\sqrt{2}}\cdot \vec{r}-(3\times 10^{12})t\right]$
   2. B.$\frac{E_o}{C}\frac{(\hat{i}-\hat{j})}{\sqrt{2}}\cos \left[10^4\frac{(\hat{i}-\hat{j})}{\sqrt{2}}\cdot \vec{r}-(3\times 10^{12})t\right]$
   3. C.$\frac{E_o}{C}\hat{k}\cos \left[10^4\frac{(\hat{i}+\hat{j})}{\sqrt{2}}\cdot \vec{r}+(3\times 10^{12})t\right]$
   4. D.$\frac{E_o}{C}\frac{(\hat{i}+\hat{j}+\hat{k})}{\sqrt{3}}\cos \left[10^4\frac{(\hat{i}+\hat{j})}{\sqrt{2}}\cdot \vec{r}+(3\times 10^{12})t\right]$
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   Answer: A

4. Q512018 · 15 Apr 2018 · Shift 1
   
   1. A.$\frac{8N{\mu }_{0}I}{5^{1/2}R}$
   2. B.$\frac{8N{\mu }_{0}I}{5^{3/2}R}$
   3. C.$\frac{4N{\mu }_{0}I}{5^{1/2}R}$
   4. D.$\frac{4N{\mu }_{0}I}{5^{3/2}R}$
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   Answer: B

5. Q522018 · 15 Apr 2018 · Shift 1
   
   1. A.$1mA$
   2. B.$2mA$
   3. C.$20\mu A$
   4. D.$40\mu A$
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   Answer: A

6. Q482018 · 8 Apr 2018 · Shift 1

   An electron, a proton and an alpha particle having the same kinetic energy are moving in circular orbits of radii $r_e,r_p,r_{\alpha }$ respectively in a uniform magnetic field B. The relation between $r_e,r_p,r_{\alpha }$ is:

   1. A.$r_e<r_{\alpha }<r_p$
   2. B.$r_e>r_p=r_{\alpha }$
   3. C.$r_e<r_p=r_{\alpha }$
   4. D.$r_e<r_p<r_{\alpha }$
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   Answer: C