IIT JEE Advanced & Mains Physics 2018 : Electricity : Rank file / expected questions : III

IIT JEE Advanced & Mains Physics 2018 : Electricity : Rank file / expected questions / Physicsmynd Elite Series  /  Page  III 

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19]  A cone [ of resistivity \rho ] is cut off at a height of h from it’s base.If it’s uniformly charged throughout it’s  cross-sections, then the resistance between the two end of the cut – off cone is –

A ]  \frac {\rho h}{\pi ab}

B ]  \frac {\pi h}{\rho ab}

C ]  \frac {\rho }{\pi h}

D]  \frac {\pi ab}{\rho h}

20 ] A charge distribution produces an electric field \vec{E}=\frac {{E}_{{0}}}{{r}^{{2}}}{e}^{{-r∕c}}\hat{r}  where c is a constant. Then the total charge in the distribution is – 

A ] 4\pi {E}_{{0}}{e}^{{\frac {R}{c}

B ] 2\pi {E}_{{0}}{e}^{{\frac {R}{c}

C ] \frac {Q}{{\epsilon }_{{0}}}

D ] \frac {4Q}{{\epsilon }_{{0}}}

21 ] Figure below shows the path of an electron where A B – when not under the influence of a field and B’ , C’ and D’ ,under the influence of three different electric fields 1 , 2 ,and 3 respectively . . Then the Drift Velocity of the electron under the second field is indicated by –

A ] AB + AB’

B ] ABB’

C ] AD’ –  AC’

D ] BC’

22 ] Earnshaw’s law states that a collection of point charges cannot be maintained in a stable stationary equilibrium configuration solely by the electrostatic interaction of the charges .Give a simple non-mathematical proof for the same . 

23 ] Two conductors are embedded in a material of conductivity {{30}}^{{-4}}\omega /m and dielectric constant \epsilon =90{\epsilon }_{{0}}. The resistance between the two conductors is found to be {{30}}^{{5}}\omega. Find the magnitude of the capacitance between the two conductors .

24] Figure below shows an hypothetical infinite conducting plane in the ( x,y,z) plane having charges Q1 , Q2 , Q3 , Q4  located in cavities.What can we predict with certainty regarding the nth cavity containing charge Qn ?

A ] V experienced by Q1 will influence the V of Qn

B ] V  of Q1  = V of Qn

C ] The whole conducting surface up to that containing Qn is an equipotential .

D ] V of the conducting plane cannot be zero .

25 ] Parallel to ( x ) and at a distance d .above a grounded conducting plane ( xy ) is placed an infinite wire of uniform charge  \lambda Then the  potential in the region above the plane is – 

A ] V   =\frac {\lambda }{4\pi {\epsilon }_{{0}}}In\{{\frac {{y}^{{2}}+{{\left({z+d}\right)}}^{{2}}}{{y}^{{2}}+{{\left({z-d}\right)}}^{{2}}}}\}

B ] V   =\frac {\lambda }{4\pi {\epsilon }_{{0}}}In\{{\frac {{y}^{{2}}-{{\left({z+d}\right)}}^{{2}}}{{y}^{{2}}-{{\left({z-d}\right)}}^{{2}}}}\}

C ] V   = \frac {\lambda }{2\pi {\epsilon }_{{0}}}In\{{\frac {{y}^{{2}}+{{\left({z+d}\right)}}^{{4}}}{{y}^{{4}}+{{\left({z-d}\right)}}^{{2}}}}\}

D ] V   = \frac {\lambda }{2\pi {\epsilon }_{{0}}}In\{{\frac {{y}^{{2}}-{{\left({z+d}\right)}}^{{4}}}{{y}^{{4}}-{{\left({z-d}\right)}}^{{2}}}}\}

26 ]  In the above case,the charge density  \sigma induced on the conducting plane is – 

A } -\frac {\lambda d}{\pi \left({{y}^{{2}}+{d}^{{2}}}\right)}

B ]  -\frac {\lambda d}{\pi \left({{y}^{{4}}+{d}^{{4}}}\right)}

C ]  \frac {\lambda d}{\pi \left({{y}^{{2}}+{d}^{{2}}}\right)}

D ] \frac {\lambda d}{\pi \left({{y}^{{4}}+{d}^{{4}}}\right)}

27 ] Diagram below represents a hollow conductor on which a test potential of around 90,000 V is applied.Choose the graph which correctly represents the incidence of potential inside the cavity . The x axis denotes the time elapsed in pico -seconds . 

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