Download App

STD 12 - 2. Electric potential and capacitance — JEE STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceJEESTD 12 - 2. Electric potential and capacitance4 Marks
MCQ
A solid spherical conducting shell has inner radius a and outer radius $2a$. At the center of the shell is located a point charge $+Q$. What must the excess charge of the shell be in order for the charge density on the inner and outer surfaces of the shell to be exactly equal ?
  • ✓
    $-5Q$
  • B
    $+3Q$
  • C
    $-4Q$
  • D
    $+4Q$
✓

Answer

Correct option: A.
$-5Q$
a
$\frac{\mathrm{Q}+\mathrm{q}}{4 \pi(2 \mathrm{a})^{2}}=\frac{-\mathrm{Q}}{4 \pi \mathrm{a}^{2}}$

$\frac{\mathrm{Q}+\mathrm{q}}{4}=-\mathrm{Q}$

$\mathrm{Q}+\mathrm{q}=-4 \mathrm{Q}$

$q=-5 Q$

Need a full question paper?

Generate a complete, print-ready paper with questions like this in minutes — across 16+ boards, with answer keys.

Start Generating Free

Explore more

JEE STD 11 Science question papers→Gujarat Board STD 11 Science question papers→Gujarat Board question paper generator→

Similar questions

If the density of the earth is doubled keeping its radius constant, then acceleration due to gravity will be ........ $m/s^2$. $(g = 9.8\,m/sec^2)$
→
As shown in the figure, after passing through the medium $1$. The speed of light $v _{2}$ in medium $2$ will be$.....\times 10^{8}\,ms ^{-1}$  $\left(\text { Given } c =3 \times 10^{8} ms ^{-1}\right)$
→
In a Young's experiment, two coherent sources are placed $0.90\, mm$ apart and the fringes are observed one metre away. If it produces the second dark fringe at a distance of $1\, mm$ from the central fringe, the wavelength of monochromatic light used would be
→
Standing waves are produced in $10 \,m$ long stretched string fixed at both ends. If the string vibrates in $5$ segments and wave velocity is $20 \,m / s$, the frequency is ....... $Hz$
→
In a pure inductive circuit or In an $ac$ circuit containing inductance only, the current
→
Consider the shown arrangement. Assume all surfaces to be smooth. If $N$ represents magnitudes of normal reaction between block and wedge, then acceleration of $M$ along horizontal equals
→
$A$ total charge $Q$ flows across a resistor $R$ during a time interval $= T$ in such a way that the current vs. time graph for $0 \rightarrow T$ is like the loop of a sin curve in the range $0 \rightarrow \pi$ . The total heat generated in the resistor is
→
The current density in a cylindrical wire of radius $4 \; mm$ is $4 \times 10^{6} \; Am ^{-2}$. The current through the outer portion of the wire between radial distance $\frac{R}{2}$ and $R$ is $\dots \; \pi A .$
→
An inductor of $10\, {mH}$ is connected to a $20\, {V}$ battery through a resistor of $10\, {k}\, \Omega$ and a switch. After a long time, when maximum current is set up in the circuit, the current is switched off. The current in the circuit after $1\, \mu\, {s}$ is $\frac{{x}}{100}\, {mA}$. Then ${x}$ is equal to ...... .

(Take $\left.{e}^{-1}=0.37\right)$

→
The surface of a planet is found to be uniformly charged. When a particle of mass $m$ and no charge is thrown at an angle from the surface of the planet, it has a parabolic trajectory as in projectile motion with horizontal range $L$. A particle of mass $m$ and charge $q$, with the same initial conditions has a range $L / 2$. The range of particle of mass $m$ and charge $2 q$, with the same initial conditions is
→