JEE Main Physics - Electrostatics
Exam Duration: 60 Mins Total Questions : 30
A charge +q located at O is placed midway between two charges of +q each.All the three charges lie on a straight line. The charge at O
- (a)
will be in unstable equilibrium
- (b)
will be in stable equilibrium
- (c)
will not be in stable equilibrium
- (d)
will move laterally along the right bisector of the line
The variation of potential energy V(r) as a function of distance of separation(r) for a proton p and an electron e is given by the graph
- (a)
- (b)
- (c)
- (d)
A parallel plate capacitor has charge +Q and -Q on its plate.The separation between the plates is doubled
- (a)
charge on the plates is reduced to half
- (b)
capacitance is doubled
- (c)
Potential difference between the plates is doubled
- (d)
Electric field between the plates is reduced to half
How many time constants must elapse before a capacitor in an RC circuit is charged to within 1% of its equilibrium charge?
- (a)
0.868
- (b)
2
- (c)
1.152
- (d)
4.606
Three identical small balls, each of mass m=2g, are suspended from a fixed point by three non-conducting threads, each with a length of 50 cm and negligible mass. At equilibrium the three balls form an equilateral triangle with sides of 30 cm.the common charge q that is carried by each ball is
- (a)
0.204\(\mu C\)
- (b)
\(0.20\mu C\)
- (c)
\(0.408\mu C\)
- (d)
\(0.306\mu C\)
Choose INCORRECT statement
- (a)
Charge is quantitised
- (b)
Charge is conserved
- (c)
Nuclear force is charge dependent
- (d)
Fraction of electronic charge may exist
If mass of electron \({ m }_{ e }=9.11\times { 10 }^{ -31 }\)kg and charge on electron,e=\({ m }_{ e }=1.60\times { 10 }^{ -19 }\)C, then the ratio of electrostatic(\({ F } _ { e }\))and gravitational(\({ F } _ { g }\)) forces that act between two stationary electrons is of the order of
- (a)
\({ 10 } ^ { 12 }\)
- (b)
\({ 10 } ^ { 22 }\)
- (c)
\({ 10 } ^ { 32 }\)
- (d)
\({ 10 } ^ { 42 }\)
Figure shows a charge +Q at a distance 2d froma charge -Q and a point P at a distance d from -Q.The field strength at p is
- (a)
\(\frac { Q }{ 4\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along BP
- (b)
\(\frac { Q }{ 36\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along PA
- (c)
\(\frac { 5Q }{ 18\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along BP
- (d)
\(\frac { 2Q }{ 9\pi { \epsilon }_{ 0 }{ d }^{ 2 } } \)along PB
Two copper spheres of same radii one hollow and other solid are charged to the same potential then
- (a)
both will hold same charge
- (b)
solid will hold more charge
- (c)
hollow will hold more charge
- (d)
hollow cannot be charged
In a non-uniform electric field, electric dipole experiences
- (a)
torque only
- (b)
torque as well as net force
- (c)
force only
- (d)
none of these
Two spheres of radii \({R }_ { 1 }and {R } {2 }\) respectively are charged and joined by a write.The ratio of electric field of spheres is
- (a)
\({ { R }_{ 2 } }^{ 2 }/{ { R }_{ 1 } }^{ 2 }\)
- (b)
\({ { R }_{ 1 } }^{ 2 }/{ { R }_{ 2 } }^{ 2 }\)
- (c)
\( { R }_{ 2 } / { R }_{ 1 } \)
- (d)
\( { R }_{ 1 } / { R }_{ 2 } \)
This question has Statement I and statement II. Of the four choices given after the statement choose the one that best describes the two statements.
An insulating solid sphere of radius R has a uniform positive charge density \(\rho\). As a result of this uniform charge distribution, there is a finite value of electric potential at the centre of the sphere, at the surface of the sphere. The electric potential at infinity is zero.
Statement I When a charge q is taken from the centre to surface of the sphere its potential energy changes by, \(\frac{q\rho}{3\epsilon_0}\).
Statement II The electric field at a distance r(r
- (a)
Statement I is false, Statement II is true
- (b)
Statement I is true, Statement II is false
- (c)
Statement I is true, Statement II is true, Statement II is correct explanation for Statement II
- (d)
Statement I is true, Statement II is true, Statement II is not the correct explanation for Statement II
The electrostatic potential inside a charged spherical ball is given by \(\phi =ar^2+b\), where r is the distance from the centre and a, b are constants. Then, the charge density inside the ball is
- (a)
\(-6a\epsilon_0r\)
- (b)
\(-24\pi a\epsilon_0\)
- (c)
\(-6a\epsilon_0\)
- (d)
\(-24\pi a\epsilon_0r\)
Let there be a spherically symmetric charge distribution with charge density varying as \(\rho \left( r \right) ={ \rho }_{ 0 }\left( \frac { 5 }{ 4 } -\frac { r }{ R } \right) \) upto r = R and \(\rho \left( r \right) =0\) for r > R, where r is the distance from the origin. The electric field at a distance r(r
- (a)
\(\frac { 4\pi { \rho }_{ 0 }r }{ 3{ \varepsilon }_{ 0 } } \left( \frac { 5 }{ 3 } -\frac { r }{ R } \right) \)
- (b)
\(\frac { { \rho }_{ 0 }r }{ 4{ \varepsilon }_{ 0 } } \left( \frac { 5 }{ 3 } -\frac { r }{ R } \right) \)
- (c)
\(\frac { 4 { \rho }_{ 0 }r }{ 3{ \varepsilon }_{ 0 } } \left( \frac { 5 }{ 4} -\frac { r }{ R } \right) \)
- (d)
\(\frac { { \rho }_{ 0 }r }{ 3{ \varepsilon }_{ 0 } } \left( \frac { 5 }{ 4 } -\frac { r }{ R } \right) \)
The potential at a point X (measured in \(\mu m\)) due to some charges situated on the X-axis is given by, V(X) = 20 / (X2 - 4) volt. The electric field E at X = 4\(\mu m\) is given by,
- (a)
\(\frac { 5 }{ 3 } V/\mu m\) and in the negative x-direction
- (b)
\(\frac { 5 }{ 3 } V/\mu m\) and in the positive x-direction
- (c)
\(\frac { 10 }{ 9 } V/\mu m\) and in the negative x-direction
- (d)
\(\frac { 10 }{ 9 } V/\mu m\) and in the positive x-direction